"WHY are people so desperate for validation they are willing to post all this personal crap to some web site?! WHY?!?"
From my perspective it's for the same reason as FriendsReunited was so popular, before the restriction on contact details for free accounts killed it. It's not about needing validation, it's about getting back - and keeping - in touch.
Last weekend I managed to get back into contact with two close, old friends with whom I'd fallen out of touch fifteen years ago, for various very good reasons. I for one am delighted.
Facebook offers a relatively safe and controlled way to get back in touch with old acquaintances, but like any security tool you need to make sure that it's properly configured.
Use of contact details is charge-free, optional, and can be restricted to confirmed friends only, so you get to weed out any crazies before letting them know where to find you. Long published lists of favourite music, films, etc provide points of (hopefully) common reference, and conversation starters.
All those add-ins aren't really my cup of tea, but it's called "playing". Friends are known to do that. You know. For fun.
Ok, so I'm rambling on a lot, but let me share one last thing with you: I recently lost my last chance to talk with another old friend. I was shy of the relative fame she'd earned since we last spoke, and kept putting off the phone call, never believing the worst would happen. Joke's on me, because it did; people that young do still die, the big killer diseases we grew up with haven't gone away. By the time I realised that I needed to get in touch *now*, it was too late - it would have been an invasion of privacy.
"...blahblahblah, so that's what I'm up to, I hear you're dying slowly of cancer, how's that working out for you? Fancy meeting up - just us, spouses & kids?"
Carrie couldn't have successfully held a Facebook account in her position, but if a quick poke & e-message had been an option then I'm pretty sure I'd have taken it.
So that's why I jumped at last weekend's opportunity. And as long as the information security is solid, I can't honestly see how anyone can justifiably criticise something that brings people together.