it just me, or are 80% of the people in the “people you may know” feature on facebook people that you do know, but deliberately choose not to be friends with?
If you can't remember someone's name then, ask them "what was your name again?" Out of instinct, they tel you their first name. Then say "Oh I knew that, I meant your last name!" And boom, you get the full name, and you're not rude. Double score.