If an actual good friend of mine deleted me, I would wonder why and contact them. But I know for a fact I've been "defriended" several times by people I once knew, or met once or twice, and I never thought about contacting them.
I want to use Facebook to share things in my life with the people I'd actually want to know things. I don't care to let everyone I've ever met, or everyone I once had a class with, or everyone I met at a party and said "we should hang out", know that we're expecting a baby or we got a new car or something.
