Oh, Facebook. You bring us so much joy, and you help us to waste so much valuable time. But you’re useful in so many ways, and you keep us connected (at arm’s reach, anyway) with a vast array of high school sweethearts that we’d otherwise never even bother to look for. But can you be more than that?It’s obvious that its creators think so, with the recent acquisition of FriendFeed and the testing of a Facebook Lite. But even still, is that the limit? Is there a limit? With Twitter and Facebook emerging as two