Facebook indicates that I have 615 friends.  Out of curiosity, I sampled 100 of these friends and determined:

Never Met - 26

Haven't seen in at least 10 years -32

In the Never Met category these "friends" share a common interest such as baseball, radio, Bob Dylan, or oldies.

The "friends" in Haven't seen in at least 10 years include people I knew in high school or college.