While I agree with most of the replies here -- Yahoo! should follow Google's lead in sharing at least the name and email address -- I can still see some value in using Yahoo!'s implementation of OpenID. It's very much like Windows Live ID's Web Authentication SDK. Both offer merely an ID, nothing more. With Windows Live, you can then fake access to such info using their UI Controls at
http://messenger.mslivelabs.com/ ... Which isn't good enough for most people who just want to skip the registration page via OpenID.
Having said that, if the focus is not on bypassing Registration, but instead to ignore all usernames and passwords for signin -- making sign-in one click -- that's when OpenID is extremely useful. Google and others have just taken it one step farther, in helping eliminate some of the Registration form.
I suppose I'll break my sign-up page in two: on the left side is "Register with your Google Account", while on the right is "Email Address", "First Name", and "Last Name", and below those 3 fields is another box with two parts. The first says, "Sign in with [Yahoo!, Windows Live!, etc.] while the second part says "Username" and "Password" for those who just want to make a local account. There'd have to be a big "OR" between each column mentioned.
Or I could make it really simple -- Google or nothing. After all, if they have a Google account, there's not much more I have to do to create their account. Anything else is just a "sign in", which still needs an account to be locally associated or created. In fact, with a Google button, the registration concept can be ignored entirely, and I can just say "Sign in with Google".
I just wish it was easier to support multiple services with info like Google currently provides. The trouble I'm now considering is how even once they login with one provider, they may want to associate other providers' accounts with their first one, meaning I'd have to merge local accunts if someone signs in with two IDs but wants one account. Oh for the good ol' days of login and password :P