You can see how we communicate it on our site if you're curious. Basically it's a modal dialog with four options:

* Facebook * Google * Twitter * Email

We don't use the persona messaging, and I think people's expectation when they click the 'email' button is that it's going to just be a normal email flow. We don't call it Persona or Browser ID or use any of their assets or messaging, because we didn't think anyone would click on it if we did.

But yes, we see a small preference for a button labeled 'email' versus facebook, and a medium preference for either over twitter.