I just deleted my Facebook account. It was pretty painless actually. First I went 24 hours without using it, then I aced it out. I had two reasons for this.
Number 1: Facebook is a huge time waster for someone like me who has poor impulse control to start with. I get obsessive about checking it every hour or so, or more. This chews up hours of valuable time I could be using for more important things like napping or taking a walk.
Number 2: Facebook has no respect for users privacy and are constantly messing with the way things work so you are forced to constantly monitor your privacy settings. Even if you do check them the meaning behind what is going on there shifts from time to time so you need to study to keep up. I have better things to do with my time than study the ever shifting privacy setting of Facebook.
I posted on FB just before I left, gave it almost an hour after that before deleting. I don't expect I'll actually miss it to tell the truth. I've deleted other things online that waste my time, email conversation lists and forums, and never really missed them after the first day or two.
Anyone who is really my friend will know where to find me here on the Angry Gnome and via my emails or phone anyway, so my experiment with "Social Networking" is over... well except for Google+ I'm still on there :-) Even though I am only following a few scientists there, no actual personal acquaintances.