Hey, I might've found something actually funny from Gamefaqs!
So on some Current Events board, a few users decided they were gonna try to catch perverts and pedophiles on adult chat rooms, ala To Catch A Predator. And once they got them going, they would ruin it by stating they were the FBI or something totally outlandish. You'd be surprised how many people they caught. This was the first, and by far the best.
http://img443.imageshack.us/img443/7479/test3hr1.jpg