For anyone who has not been keeping up with the debate on Ryan’s site this posting is going to be confusing.  Becky and I have been debating the existence of a historical Jesus and unfortunately this latest reply is turning into more of an essay than a comment so rather than post 15 comments I will be replying here.  The comments to which I am replying will be posted in red but please go to Ryan’s site to see the blog that started it all (it isn’t what you might expect) and to get the background comments that have led into this debate. 

Suetonius, a Roman historian, court official under Hadrian stated in "Life of Claudius" 25.4 "As the Jews were making constant disturbances at the investigation of Christus, he (Claudius) expelled them from Rome.(This event is also referred to in Acts 18:2) (Becky’s comment)

There is debate that Suetonius is not actually referring to Jesus in this quote.  The actual wording is “He [Claudius] banished from Rome all the Jews, who were continually making disturbances at the instigation of one Chrestus.” (The Life of Claudius).  The debate involves the spelling of the word “Chrestus.”  Although some claim that Suetonius either misspelled or was using a different form of Christ but was really referring to Jesus, others claim that since Chrestus is a correct Latin form of a true Greek name this cannot be used as definitive proof of the existence of Jesus (“Chrestus” translates into ‘Useful One’ and was commonly used to refer to slaves).  NB. The argument against the misspelling of Christ is that since Suetonius correctly spells Christians elsewhere in his writings he did not misspell the name of their supposed founder.

Another common argument against this quote is that the timelines do not add up.  The following is the footnote to this passage in the Life of Claudius:

[528]  Suetonius has already, in TIBERIUS, c. xxxvi., mentioned the

expulsion of the Jews from Rome, and this passage confirms the

conjecture, offered in the note, that the Christians were obscurely

alluded to in the former notice.  The antagonism between Christianity and

Judaism appears to have given rise to the tumults which first led the

authorities to interfere.  Thus much we seem to learn from both passages:

but the most enlightened men of that age were singularly ill-informed on

the stupendous events which had recently occurred in Judaea, and we find

Suetonius, although he lived at the commencement of the first century of

the Christian aera, when the memory of these occurrences was still fresh,

and it might be supposed, by that time, widely diffused, transplanting

Christ from Jerusalem to Rome, and placing him in the time of Claudius,

although the crucifixion took place during the reign of Tiberius.

As can be noted from the footnote Suetonius’ reference to a living person “Chrestus” occurs not only after the supposed crucifixion but also in an entirely different city.

The Wikipedia online encyclopaedia indicates that in order to take this quote as evidence of Jesus four assumptions must be made, those being:

• The "Chrestus" causing disturbance in Rome refers to a "Christ" who actually resided some years earlier in Palestine.
• The information is not secondhand via Christian sources.
• The presence of Christians in Rome by 49 implies the existence of an actual "Christ" rather than a developing legend.
• "Chrestus" means "Christ", rather than its translation "Useful One".

A satirist, Lucian of Samosata , who would have nothing to gain by mentioning and thus verifying the historicity of Jesus as he scorned Christ and Christians. "The Christians, you know, worship a man to this day , the distinguished personage who introduced their novel rites and was crucified on that account . . . . . . . . and then it was impressed on them by their original lawgiver that they are all brothers from the moment they are converted . . ." (Lucian, The Death of Peregine, 11-13)

Although Lucian mentions Jesus in “The Death of Peregrine” (a.k.a. The Passing of Peregrinus) and as you say he has nothing to gain I do not think that a reference to Christ in this piece can be treated as verifying the existence of a historical Jesus.   Although the duration and exact time of Lucian’s life is unknown his birth is placed not long before A.D. 125 which means that any reference to Jesus is not the result of personal knowledge.  Lucian would therefore have been relying on things he heard.  In this same story Lucian actually comments upon the power of the travelling word and the validity of stories.    He says “Indeed, people came even from the cities in Asia, sent by the Christians at their common expense, to succour and defend and encourage the hero. They show incredible speed whenever any such public action is taken; for in no time they lavish their all” (13) which can be read as a reference to the speed at which word travelled.  It is not hard to believe that if cities as far as Asia heard quickly the perils of Peregrine then Lucian could have heard a story almost 100 years after the supposed crucifixion.  Lucian again deals with this idea of a story much later in the text when he speaks of how he “had no end of trouble, telling the story to all while they asked questions and sought exact information. Whenever [he] noticed a man of taste, [he] would tell him the facts without embellishment, as [he has] to [us], but for the benefit of the dullards, agog to listen, [he] would thicken the plot a bit on [his] own account” (38).  Lucian notes in his own story that you cannot believe the story of a person because you never will know if he is telling it straight.  Finally, Lucian deals with the figure of Jesus directly as a story at the end of his text by writing of a “grey-haired man whose face, [he] assure[es us], inspired confidence in addition to his beard and his general air of consequence, telling all about Proteus, and how, since his cremation, he had beheld him in white raiment a little while ago, and had just now left him walking about cheerfully in the Portico of the Seven Voices,35 wearing a garland of wild olive” (40).  By mentioning the story of a man who supposedly rose from the dead and walked again Lucian may be directly drawing a parallel between his story and that which he had been told of Christ.      

Mara Bar-Serapion , a Syrian wrote a letter to his son from prison encouraging him to seek wisdom. This was written circa 70 AD: What advantage did the Athenians gain from putting Socrates to death? Famine and plaguecame upon them as a judgement for their crime. What advantage did the men of Samos gain from burning Pythagoras? In a moment their land was covered with sand. What advantage did the Jews gain from executing their wise King? It was just after that that their Kingdom was abolished. God justly avenged these three wise men: the Athenians died of hunger;the Samians were overwhelmed by the sea; the Jews , ruined and driven from their land..."

This man was quite obviously not a christian as he put Jesus on equal footing with Pythagoras and Socrates ( and also because he makes reference to polytheism elsewhere in his letter) yet his references to Christ indicate that he has no question as to wether Jesus actually lived.

Some argue that this reference to Jesus is not particularly valuable in the argument of whether or not Jesus existed.  J.P. Holding argues (in the provided link) that

We have no idea what qualifications the writer of this letter held. We are not even sure when this letter was written, other than that it was after 73 AD, and very likely after 135 AD (which fits better the description of the Jews' dispersal), but also likely no later than 165 AD (because of the description suitable to the Parthian war) [VanV.JONT, 56]. At best, it offers us a special insight into how one particular pagan viewed the person of Jesus.

Since Jesus’ name is never mentioned in the text one cannot be sure that it is to Jesus that the passage is actually making reference.  Holding notes that seven distinct criteria are mentioned in the text describing the Wise King:

• Was executed;
• Was possessed of wisdom;
• Was executed just before the Jews' kingdom was abolished.
• Was executed before the Jews were dispersed;
• Was executed by the actions of the Jews;
• Lived on in the teaching that he had given;
• Was referred to as a "king."

However, since Jesus’ name is not mentioned and there were a number of messianic pretenders at the time the argument could easily be made that the reference is to one of them (of course there would have to be documentation to support these seven criteria for any person proposed [of which there would probably be about as much as there is to support that the reference is to Jesus])

And of course there is Josephus, of whom I'm sure you've heard. He writes one passage in his "Jewish Antiquities" that has been much debated. It is believed that certain lines verifying the Messianic qualities of Jesus have been added. Yet when you take out the debated parts it still leaves us with a clear understanding that Jesus existed. The lines that are beleived to have , possibly been added are italicized: Now it was about this time Jesus , a wise man, if it be lawful to call him a man, for he was a doer of wonderful works, a teacher of such men as recieve the truth with pleasure. He drew over to him both many of the Jews, and many of the Gentiles. He was the Christ,and when Pilate, at the suggestion of the principal men among us, had condemned him to the cross , those that loved him at the first did not forsake him; for he appeared to them alive again the third day; as the divine prophets had foretold these and ten thousand other wonderful things concerning him. And the tribe of Christiansso named from him are not extinct at this day ( antiquities XVIII, 33)

As you point out there some of the lines quoted are said to be forged; however, there is also an argument that this entire passage is a forgery (some argue that it was written by Eusubius).  In 1941 John G. Jackson   wrote regarding this passage that “it is generally regarded as a forgery, even by Christian scholars. The passage is not mentioned by any Christian writer before Eusebius, in the early part of the fourth century.”  This is a significant point because Origen, compiled a list in A.D. 240 of references to Jesus and he “fails to mention it [Josephus’ passage], even though he does mention the less significant reference to Jesus, as brother of James, which occurs later in Antiquities of the Jews (book 20, ch. 9).”   

See http://en.wikipedia.org/wiki/Testimonium_Flavianum for more information.

Also , there is Pliny the Younger- who was Governor of Bithynia in Asia Minor makes reference to Christ and Christians in a letter to the Emperor Trajan circa A.D.112

Then there is Thallus , one of the first secular writers who mentions Christ in his history of the eastern mediterranean world circa. a.d. 52

Phlegon , also a secular authority , wrote a history called "Chronicles" This work was lost but parts were preserved through Julius Africanus' writings. THese writings also verify the existence of Jesus

Pliny –   To quote John G Jackson

There is no evidence that this Christ was the Jesus of the Gospels. The Emperor Hadrian in a letter to the Consul Servianus (A.D. 134), asserts that the worshippers of the sun-god Serapis, in Egypt, were Christians, and that these sun-worshippers called themselves "Bishops of Christ." The worship of Serapis was imported into Egypt from Pontus, a province bordering on Bithynia. The Christians mentioned by Pliny the Younger were in all probability worshippers of Serapis. 

Thallus -  Doubt can be cast upon the authenticity of Thallus’ writing for a number of reasons.  I will list one here, but please check out the link provided for more information.  The only information available on Thallus comes from Christian apologetic sources beginning in the late 2nd century.  In an essay on Thallus Richard Carrier notes that:

The Armenian reference places the end of Thallus' "brief compendium" at the 167th   Olympiad (which spans 112-109 BC). This would remain uncontested if it were not for a single reference to Thallus regarding an event long after that time: namely, the darkness at the death of Christ. Since this event must have occurred in the 1st century AD, and no doubt sometime between 28 and 38 AD, there are two possibilities: either the Armenian text is referring to a different work, or the date has been corrupted. Virtually every scholar to date has opted for the latter and made efforts to conjecture the original date--the only two plausible (though still unlikely) options are the 207th Olympiad (which spans 49-52 AD) and the 217th Olympiad (which spans 89-92 AD). The latter in fact is the more likely, judging from palaeography. But as I've already noted, it seems far more likely that the Armenian reference is to a different work. It could even be an excerpted epitome of a longer chronology.

This leaves us with no clue as to when Thallus wrote. Since the 1st-century darkness was probably not mentioned in the "brief compendium," there is no reason to suppose that the date of 109 BC is incorrect--there is nothing physically wrong with the text, nor any other reason to suspect an error (although Mosshammer claims otherwise, his reasoning is hard to justify). However, if Thallus did mention the darkness in another work (probably the Histories), he clearly had to have written after 28 AD. Although the guess of 52 AD as the end-date for the compedium is the one most commonly mentioned, if the date is wrong at all then 92 AD is more likely correct. But all these possible dates--109 BC, 52 AD, 92 AD--only give us the "time after which" he had to have written this "brief compendium." These dates do not tell us when he wrote the Histories or whatever work that mentioned the darkness.

It is also supposed that the final date covered by the compendium should be close to the time the compendium was written, but that also does not follow. Eusebius, for instance, wrote a world chronicle that ended some thirty years before he wrote it. Moreover, when an author writes a compendium there is no telling how much history he intends to cover, or how far back he will end it--and a work as short as three books might very well have been so short because it was unfinished. In other words, the "compendium" could have ended in 109 BC even if it was written in 109 AD, and if the compendium's end-date was 52 AD or 92 AD, it could still have been written in 109 AD, or later. So we have to look elsewhere for a "time before which" Thallus wrote. All we have is this: the first time Thallus is ever mentioned is by Theophilus, writing around 180 AD, which leaves us with over a century of grey area: Thallus could have written any time between 28 and 180 AD. And if he did not mention an eclipse occurring in the first century, then he could have written any time between 109 BC and 180 AD, a span of almost three centuries.

(Thallus: an Analysis (1999), by Richard Carrier http://www.infidels.org/library/modern/richard_carrier/thallus.html)

As for the religious text I am not going to even look at that; however, to the quote you mention ( "No serious scholar has ventured to postulate the non-historicity of Jesus." Otto Betz) I offer up this: “A thinker sees his own actions as experiments and questions--as attempts to find out something. Success and failure are for him answers above all.”

Friedrich Nietzsche, The Gay Science, section 41

NB. Please note that I inadvertently missed what you said on Phlegon and will post on that in an addendum later.

References:

All liked sites have been used and I do not feel like retyping them.  The Wikipedia on-line encyclopaedia was a surprisingly obective source.  If I missed any sources I sincerely apologize and am not claiming your research as my own