The xkcd IRC channel instituted the Robot 9000, which mute-bans anyone making an unoriginal comment.  Obviously this does not prevent trolling, but it does reduce some of the more low-hanging fruit of retardation: <a href="http://blag.xkcd.com/2008/01/14/robot9000-and-xkcd-signal-attacking-noise-in-chat/" rel="nofollow">http://blag.xkcd.com/2008/01/14/robot9000-and-xkcd-signal-at...</a><p>4chan also implemented Robot 9000 on one of their boards: <a href="http://boards.4chan.org/r9k/" rel="nofollow">http://boards.4chan.org/r9k/</a>