The identity team at Mozilla announced Beta 2 of Persona. Glad to see additional progress on this awesome distributed authentication protocol. I've been using Persona on a couple of projects and find it pretty easy to implement and users have found it easy to use. Not having to implement a password system and allowing users to use existing email addresses is a big win, in my opinion.
Here is Mozilla's announcement: http://identity.mozilla.com/post/47541633049/persona-beta-2 The embedded video is fun.
Read this interview with Lloyd Hilaiel, Persona's technical lead. Among other things, he articulates the benefits of having Mozilla provide this capability. https://blog.mozilla.org/beyond-the-code/2013/04/09/persona-beta2/
Here is a good article: https://hacks.mozilla.org/2013/04/persona-beta-2-launch/
So I misunderstood how Yahoo! was supported. The new Identity Bridging capability that Persona introduced in Beta 2 was used. Mozilla built a bridge between Persona and OAuth and OpenID, so that email providers that support those protocols out of the box can be easily added to the Persona universe. And the UX is better because when there is no longer a need to do the email confirmation dance.
Learn something every day.