These days, it seems like the immediate response to being insulted or betrayed is, "OMG I'm going to delete them from Facebook". But don't forget this saying: keep your friends close, and your enemies closer. If life is a battlefield, then for some, Facebook is the front line. Take advantage of it. You don't have to interact with your enemies (er, frenemies?), but you can use the News Feed to keep tabs on them.