I'm quite selective who I accept as a FB friend. My very minimum requirement is that they must be someone who, if I bumped into them when I'm out, I'd stop and have a good catch up with them or go for a coffee.
A close friend of mine appears to accept anyone on FB as a friend and has now got to the stage where they are befriending my close friends, who they have definitely never met (and live the other side of the country).
Personally I don't want "friends" on FB who can potentially see what I get up to when I don't even know them.
Do you have a minimum requirement?