I have old ex's and old friends on FB. So does my husband. We've been married for 33 years, and are in our late 50's. I think it is a maturity thing: maturity and confidence in self, and maturity and confidence in relationship.

We both enjoy touching base with old friends, and honestly, even old ex's (and we departed as friends mutually) are just old friends after decades.

Neither of us have hundreds and hundreds of friends on FB, but we both probably have a bit over 100 each: many of them are relatives (probably the bulk of the people we interact with most often); the next group is current friends/coworkers; and finally, those old high school and/or college friends that we just like to sort of keep up with. It isn't that we are buddies or anything, but we come from a shared background, geography, etc. and as you get older, that shared history becomes important.