FB has let me find people from my old high school that I always wondered about but of which I have completely lost track. Sounds like an ad for FB, but it was pretty cool to get to talk to someone I haven't spoken with for 14 years.
I love the security stuff because once my mother figures out how to create an account, I'll definitely want to weed out what information makes it her way.
It is also fun when the VP of Client Services comments on your FB status... that you posted mid-work day... and she agrees with it.