I've taken to literally ignoring friend requests. I don't mean hit the "Ignore" button, I mean I leave them sitting there, forever pending. They can't send a new one if the last one is still pending.

Right now I have four requests pending. One is an EoFFer but I don't know who it is, two are my stepmother's mother's cousins (wtf?), and one is a girl who invited herself and her boyfriend to my wedding and then didn't show up.