It uses your email address, and seems to offer a good way to get access to an OpenID-like sign in (maybe this is using OpenID or OAuth under the covers?)
It looks like WebFinger is not really an authentication system but functions more like a user profile. It lets someone know what music you listen too, or what programming language(s) you know but it doesn't prove that you are you.
http://www.readwriteweb.com/archives/google_enables_webfinge...
It uses your email address, and seems to offer a good way to get access to an OpenID-like sign in (maybe this is using OpenID or OAuth under the covers?)