We've tried to delegate login credentials among openId providers like Google and MyOpenId.com. However, once claimed, a site becomes tied to just one. This has been brought home after MyOpenId.com went offline February 4th and remains offline two days later.
MyOpenId.com is a service provided by Portland company Janrain. In 2011 they claimed that the future for openId is bright. blog
I tried to call Janrain support but could not talk to a person. I finally posted a complaint to twitter suggesting that I'm made a mistake to rely on Janrain. They picked up on this and had the service running in ten minutes.
I built OpenId into wiki and used @Janrain for login. Now, two days without service I have to reconsider that decision.
Our @Janrain experience reminds us why wiki must be federated. Video chat on the subject starts in 10 min.
We could support IndieAuth which uses a page of rel=me links to other authenticating services to aggregate trust alternatives. website
We could support Mozilla's Persona which uses multiple email addresses as the basis of validation. website