Facebook is hardly a complete waste of time.
The basic functionality (events, keeping people connected... are amazing). People who would never have organized things online, now use facebook events with ease.
The applications...well they can be a bit of pain. I don't use any of them, except the games, though i have been tempted by the occasional gimmick app. That said, the applications are what will keep facebook from going to the dumps. Poker, scramble... are great simple games that keep people coming back/wasting time.
But platform is amazing. The userbase is equally impressive. I often see this as being the most untapped power of facebook.
I mean, say you're looking for places to eat. There are a million and one restaurant review places on the internet. But with the power of facebook, you have a platform where you can 'trust' your friend's opinion. Especially considering they are local. This trust becomes implicit and there's no need to generate yet another account. It's an implicit OpenID.
Not sure how it would apply to sites like this. But maybe it could connect to facebook's userbase and you could 'see' what your friends or friends of friends have rated. This would help cut down on 'spam'. It would certainly be a lot more reputable than the 'wisdom of crowds' that seems to be everywhere, but is increasingly being taken advantage of by organized groups. of course, nothing stops both both methods from being employed. A global rating, and then a 'your friends rating'