Portrait of the Modern Terrorist as an Idiot by Bruce Schneier:

So these people should be locked up … assuming they are actually guilty, that is. Despite the initial press frenzies, the actual details of the cases frequently turn out to be far less damning. Too often it’s unclear whether the defendants are actually guilty, or if the police created a crime where none existed before.

The JFK Airport plotters seem to have been egged on by an informant, a twice-convicted drug dealer. An FBI informant almost certainly pushed the Fort Dix plotters to do things they wouldn’t have ordinarily done. The Miami gang’s Sears Tower plot was suggested by an FBI undercover agent who infiltrated the group. And in 2003, it took an elaborate sting operation involving three countries to arrest an arms dealer for selling a surface-to-air missile to an ostensible Muslim extremist. Entrapment is a very real possibility in all of these cases.