Although I've got nearly 300 FB linkages, I'm still in the 80%+ category. I joined primarily because club event notices were posted there.
Over 1/4 of the 300 are family, and given reunions and funerals, I've seen pretty much all of them within the last 5 years (there are still a few dead ones in there though).
40% are people I've seen recently from the social events I attend (clubs) that haven't moved away, or lost interest in the clubs.
35% are people I probably will never see again(PNSA), but only about half of those are older than 5 years, so the answer to the poll came in at 85% in the last 5 years.
Of the PNSA, there are one or two that I've never met in person, and a couple of high school friends. But the majority of the PNSA crowd were previous club members that fell-out. The rest were people I met traveling and we exchanged pictures. Facebook doesn't load me with those folks' posts, but when it does give me one, usually it's interesting (they're traveling again). I don't toss these aside...you never know when you'll need some local G2, and having people all over the place that remember you and that you can ask about something in their geography is kind of nice.