I don't really particularly want family members on my Facebook, either. My online and familial personas colliding? What is this, an episode of Seinfeld?!
My mother-in-law sent me a Facebook "friend" request... I didn't know how to respond. You know I had to explain to my wife why I wasn't "friending" her mother. That didn't go so well.
My 20 year old added me to his Facebook friends then proceeds to nag about how the party they were just at didn't have enough beer or whatever... Um, I can read this you know son...
So, it's good I can keep track of him that way... :)