I just met Alex Jacobs this morning. He told me within hours his new protocol for identity would be live within hours. It is now live.
It uses e-mail addresses (like so many sites) but users only have to authenticate their e-amil once.
How it works
1. User give you their email address e.g. email@example.com.
2. You post the email address, requested data, and a secret confirmation URL to the users mail domain e.g. in python: (see there site)