I don't get it...

I've had a few people talk to me about opening a facebook account.  But I just don't get it. Can someone please help me understand Facebook?  So you go on the computer and communicate with your friends and get in touch with friends from the past.  I guess my question comes because a few months ago my former sister-in-law emailed me and told me a friend of mine was trying to get a hold of me.  It was a male friend of mine from EAC.  He looked up Becca Terry in Peoria and came up with her thinking it might be me.  This guy was a great friend of mine, we never dated, just friends.  His facebook picture was him with his wife and little baby.  I went on his facebook and could see that he had other people from EAC on there.  But seriously, am I really interested in getting in touch with all of these people?  A year and a half ago we had an EAC reunion.  I was on the committee and we sent out about 500 invitations (actually I have no idea how many we sent out but it was a lot) and only about 40 people and their spouses came.  So if everyone is so interested in keeping in touch why didn't they come to the reunion?  Maybe it was a bad weekend or too far to travel or too expensive. Dave has never mentioned anything about facebook but I can't imagine myself saying "Oh sure sweetie, go ahead and accept all of the girls from your past as friends, I'd like to know what they are up to too."  And no this isn't a trust or loyalty issue I just don't see how that is a good idea.  On the other hand, I'd love to get in touch with some of my old roommates that I'm sure are on facebook.  So, I guess I could accept the girls as friends and tell the boys to bug off and go hug their wife.  But then that would come across rude because I know their intentions would be totally innocent and they would think holy cow who does she think she is?  Ok, so this might all stem from some counsel I heard a long time ago and I don't remember who said it but it was someone of significance.  They just counseled that we not keep in touch with past boy/girlfriends after marriage.  But then again people change.  But then again it is good counsel.  Anyway I have rambled off way too long about a subject that may have offended some people since everyone has a facebook account (of which I have no idea who you are because I don't have one).  And maybe I'm just jealous of facebook because I feel so out of it since I don't have an account.  Hopefully I don't sound too negative.  I really am a "glass is half full type person".  But I just don't get it.