Google is trying to reinvent (re-born) finger protocol. And use email address as a key point for user info. See here. But there is a very interesting quote:
"People have been trying to use URLs as identifiers for people (as OpenID does), as it has great readability/discoverability properties, but this effort has largely failed because of UI/UX design failings, user confusion about URLs, etc."
So, the OpenID father Brad Fitpatrick says that OpenID largely failed?