Comment Re:I disagree (Score 3, Interesting) 549
We do, it's called Open ID, which is what Google leverages for their single-signon (not sure if FB is their own solution or not). It was a really popular thing about 5-10 years ago and got a ton of attention. I think even MS enabled it.
The problem with it is this: everyone was willing to let open their servers be the authenticating source for OpenID, but no one was willing to trust a 3rd party's servers to do the same.
So I can create identity authentication galore at mydomain.example.com, but if Google isn't willing to trust mydomain.example.com, then it's not very useful as a unified login authenticator.