Marc Lynch studies Al-Qaeda's relationship to technology:
...one of the biggest problems for a virtual network like AQ today is that it needs to build connections between its members while protecting itself from its enemies. That's a filtering problem: how do you get your people in, and keep intelligence agents out?
An AQMonster.com database would be easy pickings - an online list of all the 'explosives experts' would be a gift to intelligence, no? An AQFacebook or AQSpace might create an identifiable universe of jihadist sympathizers, but again would probably help intelligence agencies as much as AQ. Perhaps an AQLinkedIn model, where members need to be recommended by a current member would reproduce the low-tech approach of allowing in trusted members and keeping out unknown quantities. This could potentially strengthen the 'organization' part... but at the expense of a greater distance from the pool of potential recruits who would not be sufficiently trusted to join. Overall it's hard to see how AQ could adapt social networking without creating such vulnerabilities. Its rivals, on the other hand, have no such problems - Muslim Brotherhood youth are all over Facebook.
(Hat tip: Noah Shachtman)