That's not to say there isn't value in that. I've been really happy to connect with old acquaintances over just a message or two. I don't really want much more contact than that.
I get what you are saying. The one good thing about Facebook is that it took a lot of that fluff out of my inbox. But could I not have learnt to manage/gloss over it?
The thing that Facebook does well - is tracking down contacts - to add to your 'address book.' It's not so easy in the world of email. That's because we aren't publishing our address books publicly (probably for good reason.)