I've seen a few demos of this. The developer story is great.
Easy to integrate, no need to worry about screwing up storing passwords and you are not abdicating authentication to some evil or possibly evil in the future, company.
Not trying to troll or anything, but how do we know Mozilla won't be evil in the future? I'm sure you could find people who thought that about Google back in the day, they seem to now be routinely called out for questionable evils.
AFAIK Right now there are two things that Mozilla controls.
1) login.persona.org that takes care of authentication
2) a JavaScript shim that developers add to their sites to get the login button to work.
Persona is designed in such a way that reliance on Mozilla will be phased out as email providers take care of #1 and as browsers start to implement #2. As of now I think FireFox is the only browser that has #2 baked in.
Actually, only FirefoxOS has #2 baked in. Everything else is using the shim.
I'm pushing us to get our data formats stabilized in the next few months so that we can start building native extensions for browsers and get ourselves completely out of that loop.
It's worth thinking of Persona as the reference implementation of the BrowserID protocol. If we're successful, Persona as you know it automatically disappears as more and more domains and browsers add native support for the protocol. :)
Mozilla is a global non-profit organization dedicated to building a public good -- an Internet that works for everyone.
Google is a giant multi-national corporations that measures revenue in the tens of billions of dollars per quarter.
That means that Mozilla's responsibility is to the people of the world and Google's responsibility is to maximize financial returns for the the already well-off financial class that invested in Google stock.
Easy to integrate, no need to worry about screwing up storing passwords and you are not abdicating authentication to some evil or possibly evil in the future, company.