As much as I'm not a fan of FB re all the privacy stuff (not to mention a history of horribly under/wrongly-documented and semi-broken APIs), it's done wonders for a large generation of web users in terms of allowing them to easily (and consistently) share their lives with a lot of their friends and family. I see that aspect as a good thing.
I'm not for or against FB; it's not my cup of tea, but I might not be like the typical user. What I don't understand is the 'forced to use facebook' meme that comes up every time someone is unhappy with some changes there.
If I wanted to share a picture with 12 people, I had to send 12 emails, or CC 12 people, or BCC them because they didn't want their emails shared with people they didn't know.
Not everyone understood IM, and not everyone was on at the same time.
The bigger question would be why more people didn't latch on to friendster or myspace before facebook. It's as much a social trend as much as a technical one. As computers got cheaper and more people got net connections (or faster ones), there was more of a need/demand for sharing info. Facebook hit at the right time to capitalize on network effects amongst 'regular' folk.
Unless your friends are conveying intellectual stimulation that stands on its own, you're just reminiscing and should probably just some make new friends and call your mom now and then.