So come on then Danny why don't you insist upon personal details when people sign up for a user name?
Surely that would reduce the need for greater bandwidth, advertising etc. It wouldn't decimate the site, just get rid of the idiots and libelers.
I for one would gladly give my details so long as I could be assured of anonymity, except for the case when you are forced to give them by a legal body if I had libeled someone.