Seriously, though, the biggest argument in favor of it that I hear is event invitations. But think about it, if the most effort that somebody can put into inviting you to their event is clicking a button to "send to all", they don't really value your friendship. I don't have a Facebook account, and when people invite me to something, they send a personal message that signals they actually value my friendship and want me to attend. As someone on the Internet said, Facebook maintains friendships in a persistent vegetative state.