A networking site much like Myspace that lonely people go to and add random people as friends since they don't have any in real life and then try to brag to everyone about how they have 3000 friends. But nobody gives a shit.
Bob: Ew, look, it's that loner Ryan.
Andy: What do you mean, I heard he has like 10000 friends.
Bob: On Facebook.
Andy: Oh what a fag. Let's go take a shit on him.