MockMyID was a Mozilla Persona Identity Provider (IdP) that would gladly issue assertions to anyone and everyone, without a second thought.
It was like Mailinator, for Persona.
(All email sent to mockmyid.com addresses was delivered and readable at Mailinator!)
MockMyID made it easy to test and demo sites that use Persona.
Whenever you were asked to log in with Persona, you could just make up any email address you want