<human>: Bloggingheads.tv (sometimes abbreviated "bhtv") is a political, world events, philosophy, and science video blog discussion site in which the participants take part in an active back and forth conversation via webcam which is then broadcast online to viewers. The site was started by the journalist Robert Wright (The Evolution of God, Nonzero: The Logic of Human Destiny, The Moral Animal) and the blogger and journalist Mickey Kaus on November 1, 2005. (Kaus has since dropped out of operational duties of the site as he didn't want his frequent linking to be seen as a conflict of interest.) Most of the earlier discussions posted to the site involved one or both of those individuals, but since has grown to include a total of over one thousand individual contributors, mostly journalists, academics, scientists, authors, well known political bloggers, and other notable individuals.

Although most episodes and matchups do not occur on any kind of a regular basis, there are a few notable exceptions to this. There is a frequent (previously biweekly and weekly, but now less frequent) diavlog matchup between the two co-founders of Bloggingheads.tv, Robert Wright and Mickey Kaus, generally related to politics in some form, that usually occurs on either Wednesday or Thursday. While some of the other diavloggers are frequently matched against each other (e.g. David Corn & James Pinkerton) there is usually not a regularly scheduled time at which they take place.  "Science Saturday" was the name given to the weekly episode appearing on Saturday that was always science related. Its last episode was released on December 24, 2011. It usually (but not always) involved either one or both of the science writers John Horgan and George Johnson. Many well-known people in the science community were a part of Science Saturday, including Michael Shermer of Skeptic Magazine, biologist PZ Myers, Craig Venter of the Human Genome Project, aging researcher and biogerentologist Aubrey de Grey, and philosopher David Chalmers, among many others. However, in September 2009, four high-profile science bloggers who had previously participated in Bloggingheads.tv discussions publicly distanced themselves from the site and stated they would no longer agree to appear in Bloggingheads.tv segments. The scientists - Sean Carroll, Carl Zimmer, Phil Plait and PZ Myers - all criticized what they claimed was a policy by Bloggingheads.tv to provide a platform for the anti-scientific ideology, Creationism without an opposing point of view for balance. PZ Myers said: "[Bloggingheads.tv] was setting up crackpots with softball interviews that made them look reasonable, because their peculiar ideas were never confronted."  "The Week in Blog" was a weekly segment which normally appeared on the site on Fridays. Its last episode was released on March 7, 2012. The format was to discuss what has showed up on the past week on both liberal and conservative blogs, from both a liberal and conservative viewpoint. The three regular hosts of "TWIB" were Bill Scher of Liberal Oasis, Kristin Soltis of the Winston Group, and Matt Lewis of The Daily Caller. Original host Conn Carroll of The Heritage Foundation stepped aside in early 2009. Guests who appeared on the show are Armando Llorens (of Daily Kos), Amanda Carpenter, and Nate Silver (of FiveThirtyEight) among many others. CANNOTANSWER

What were the regular segments?
<bot>: There is a frequent (previously biweekly and weekly, but now less frequent) diavlog matchup between the two co-founders