Or give up closed, centralized systems altogether and take a look at Mozilla's Persona project -- the open web deserves open, federated authentication systems.

Or give up closed, centralized systems altogether and take a look at Mozilla's Persona project -- the open web deserves open, federated authentication systems. (N.B.: I work on Persona, and it does have a centralized fallback for bootstrapping browsers and identities. The difference is that the centralization is temporary, optional, and automatically goes away over time.)