To me, Persona never _shipped_. They still discourage self-hosting the identity verification code, so even on a happy path where the user somehow managed to ge

To me, Persona never _shipped_. They still discourage self-hosting the identity verification code, so even on a happy path where the user somehow managed to get an email provider that natively supported Persona you still had to talk to Mozilla servers. That's not federated identity, it's centralized; it offers nothing above Facebook Connect. Would doing that alone have made Persona a success? Probably not. But as it is, it's not even in the running. (Context: I wrote my own IdP, so in theory I could have been on that happy path.)