> For most users I talk to, an email address (rather than a URL)
Hits nail on head. It's unbelievable how dumb geeks who try to design UX experiences can be (and I say this as one of them). The first day I saw OpenID I was amazed that anybody would try and use a URL as an identifier.
Why would anybody put something that no normal person understands front and center of their UX? This is like opening a shoe shop and putting a quiz about 2nd order differential equations on the front door. Guess what - nobody is going into your store!!!
It was already a huge challenge to get people to understand the concept of using a login from one site to login to another. But it was doomed from the start the minute someone said you should have "http:// in front of your username.
