That army is also on Twitter, Tumblr, Google+, Wordpress, LiveJournal, MySpace, and any other free website that allows them to publish themselves for others to publicly see. That doesn't mean that those services aren't useful to those of us who have friends that aren't narcissists.
If your Facebook news feed (or your Twitter stream, or whatever else) is full of nothing but self-indulgent crap, then maybe you should find some better people to be friends with?