They do troll facebook pages and go after people I know this for a fact. It was admitted at a circuit assembly. When Myspace was all the rage, my PO came up to me, (I was a MS back then) and asked me if I had a myspace account. I did not, and I told him that.
Then he asked me if others in the hall did, and i said I guess some of them do. Next, he asked me if I could help him find the young ones myspace page to see what kind of things they were putting up on it. I told him that since I didn't have myspace he was asking the wrong person and that I did not feel comfortable spying on people. I'm sure he must have found someone else because I knew of kids that got in trouble for things that were on their myspace page. I'm sure they still do the same thing with facebook.