I've been using FB for connecting with my RPG group (we've been playing Eclipse Phase via Skype. It's awesome). People generally post songs and stuff from 9gag and the like. It mostly falls under either of those categories. I once made the mistake of getting into a discussion about space exploration on FB: Someone posted this letter of note, which encourages space exploration, and the person disagreed with it. I had a terrible time making myslef clear. FB wasn't made with long discussions in mind: the lack of markup makes it quite clear. Also, you can't search updates, which makes them disposable. You can always use the hide option: it lets you sort what types of updates you get from your friends (Photos, games, comments, music etc.) without having to unfriend them.
Discuss with your RPG group on Hubski I quit using FB for a while because a higschool girlfriend started posting hateful things about homosexuals. I unfriended her because I would rather remember her as she was prior to having been corrupted by anger and well... religion. But I've been creeping back on the FB as my family and friends request photos of my daughter. I live away from all of them now and they don't see her regularly. I have found myself trying to use Hubski markup on FB comments ;)