While I like the idea of Gravatar (a single avatar that can be queried/used by a number of web services), why make me create a globally unique username. I thought it was already established that globally scoped usernames were a bad idea. Surely my email address would be just fine (sadly usernames can only be alphanumeric). Maybe it's a bit petty (not wanting to create another username), but it does annoy me that a number of services now only support Gravatar.

I wonder if OpenID could also support this kind of use-case. Then I'd host my avatar wherever I pleased.