Facebook is like the on-line version of a high school reunion. You know, suddenly all these folks you haven't seen or spoken to in like decades have a ton of things to say to you, of which a tiny few are mildly interesting. But the ones that you mostly "talk" and "banter" with are the ones that you see more often in real life anyway! They're like your guests that you drag to the reunion so that you have someone to talk to while you're there.
Course there are two main differences. High school reunions happen every 10 years whereas you can never leave FB if you wanted to. Though you can ignore certain comments and chat invitations and those folks never know it.
Maybe I'll carry a little sign with me that says "offline" to tape to my forehead if a party I'm at turns bad.