This raises some big questions. For a start, the same paper also suggests "disruption" of the sites. This, of course, is tantamount to censorship. It also raises the problem of disrupting the sites you are watching for intelligence and hence blinding yourself. But there's a more important point than either this or the usual civil-liberties/digital rights arguments. The leaked document sounds a tad, ah, limp, doesn'it? Are we really thinking of using the limited supply of agents with the knowledge of Arabic (and perhaps more importantly Urdu and Punjabi), Islam, jihadi politics, and the streetsmarts to pass on a jihadi forum to attempt individual conversions of random forum posters? Seriously, I wouldn't think there were more than 200 suitable agents in the services. It doesn't sound like a great return on investment.
I can guess what, say, the Office of Sleazy Intelligence would have done in this situation. They wouldn't be trying to talk the buggers down. They would probably be the most extreme extremist in town, doing their best to wind up the others into saying things outrageous enough to provide a pretext to shut the site down and arrest everyone they could catch. If you're going to have agents, they might as well be agents provocateurs. Otherwise you're casting your bread on the waters with little chance of success.
That sounds all well and good - until you remember Joseph Conrad's Secret Agent.
"That the spy may fabricate his information is one thing, but in the field of revolutionary action he may be tempted to fabricate the facts."Not that we'd actually start letting off bombs, but if you were trying to get them to discredit themselves, there's a serious risk that you might inspire them faster than you gathered evidence to lock 'em up.