Say good-bye to passwords?

So I've been thinking about the idea of using public keys instead of passwords to gain entry into web sites. It has the advantage that users don't have to remember anything but their email address (if that!). I think it's also more secure. I've written a semi-informal paper about it, and I'd appreciate comments from both the tech-savvy (who can speak to the security) and not-so-sophisticated (who can speak to usability).