The act or practice of de-friending people on Facebook, mainly due to excessive status updates. Although this may apply to the de-friending of individuals, it more commonly refers to going through one's "Friends" list and removing a relatively large number of people, such as people you met at a party once and haven't seen since, friends of exes, and high school classmates that you actually kind of hated.
I just did a Facebook audit and got rid of like fifty friends. I didn't even know who half of those assholes were.
1. Acting like a complete douchebag in a way only possible on Facebook. This might involve relatively innocuous things like Facebook stalking or being a Facebook whore, or it might be a little more obnoxious, like telling Friend A that you can't go out on Saturday night and then posting tons of pictures from Friend B's party the next morning.
2. The innate quality of Facebook that inspires this sort of behavior.
"Why does his ex-girlfriend keep writing cute little posts on his wall? Do you think they've still got something going on?"
"Honey, don't worry about it. It's just Facebook fail."