Some members of Anonymous now believe that Operation AntiSec, the hacking movement started last summer with goal of hitting major government and corporate targets, was a trap created and supervised by the FBI and recently-outed informant Hector "Sabu" Monsegur.
YourAnonNews has created a detailed timeline to prove their point, but the key fact is that Sabu was arrested on June 6, 2011, and returned to the Internet weeks later to announce the formation of AntiSec, billed as a joint venture between Anonymous and Sabu's Lulz Security.
The timeline lists several AntiSec attacks that Sabu participated in or directly encouraged after he had signed a plea bargain promising to "commit no further crimes," and YourAnonNews's conclusion is that all of those attacks were carried out under FBI supervision.
Now that Sabu has been revealed as an informant, his repeated calls for fellow hackers to join the #AntiSec IRC channel now seem like attempts to lure them into an FBI-monitored trap.
Although the sequence of events may not be hard evidence that AntiSec was entirely an FBI invention, it's hard to imagine Sabu getting away with it post-arrest if he didn't have the approval of his federal handlers.