[callahad]

Firefox Accounts is a centralized authentication system based on email addresses and passwords. Persona is a decentralized authentication system based on proof of email address ownership.

For Sync, Persona isn't the right tool for the job. Specifically, Sync needs a human-memorable source of entropy (password), and minimal external dependencies so that recovery meets user expectations. It's possible that Accounts will eventually use Persona for email verification, but the centralized password is unlikely to go away.

Marketplace is in a similar situation, and actually uses a centralized, friendly fork of Persona so that it can proactively force users to re-authenticate before purchases and allow people to use the site before they complete their email verification. Those features might make their way into Persona in the future, but for now it felt better to trim them from Persona and switch Marketplace over to Firefox Accounts.