Uh, why are you leaving? If you can't come up with reasons yourself, why would you even do it? Pointless
I stay because I have friends that live in different cities and states that I never get to see, but love to talk to and keep in touch with. Same goes for family. But, leaving has been appealing to me because I have been harassed by quite a number of people (it happens). You should come up with your own reasons though. It is your life
You can adjust your privacy settings so you don't even show up in a search, and only your friends even know that you have a profile. So if you're leaving because you've been hassled, I'd say dial up your privacy settings and keep your fb so you can keep in touch with your friends.
Facebook is pretty boring, but I keep mine up anyway because it's one of the most convenient ways to contact people.
This. You don't have to check it everyday like its something you 'must do'. I've seen people who check their facebooks 10+ times a day just so they can know everything about everyone.
I say what others have said, boost your privacy settings, delete all the "friends" you're not really friends with and just not check it all the time. It's really convenient for organizing events like parties or study groups, and for keeping in touch with people you don't see often, so if you set up your account carefully and be more selective about your friends, it's actually kind of nice to have.