Not to "derail" the open-id idea I think we should support oAuth 100% and it certainly would help with persistent applications and scalability...
I don't think that's a derail at all. I don't know OAuth that well, but it seems to provide the same benefits of OpenID Provider.
Now... going to a 100% Ajax solution for apps... :-) Yeah, I've seen that used to solve interesting authentication & session problems. But that does limit the developer pool and range of apps that'll get built. (Witness the current scarcity of web-based auth-enabled wikimedia apps.)