The New Yorker magazine has an interesting profile of online (and offline) terrorist-hunter Rita Katz:
There are hundreds of extremist Web sites, but there is also a hierarchy: sites on which terrorist groups release statements and videos have the most devoted audiences. As soon as something appears, users post it on dozens of message boards, chat rooms, and blogs. For much of the past two years, activity centered on a board called Ansar; once it was shut down, with its British-based Webmaster imprisoned for his part in a bomb plot, users shifted to a board called Al Hesbah. There was absolutely no disruption, Katz said.
Rita runs a very small research group. By contrast, the IHT reports on the phenomenon of online mobs of vigilante Chinese chasing alleged evil-doers: more