I hate Facebook, but I do have an account (that I check about once a month or less), just in case something interesting or worthwhile turns up whenever... yeah right, but hey, you never know.
If someone wants my attention, they have my email address or phone number to get it with. Both are available on Facebook, just in case they don't already have it (only "friends" can see them, of course).
My settings are pretty damn tight in general, but not extremely, because I don't post anything so I don't care overly much.
If more people join Google+, I'll consider using that instead. Much more appealing, though I don't trust Google any more than whatever his name is (and co.)