I agree, the last thing we need is yet another silo of another third-party, single-sign on solution: but WordPress could have made a real marketplace difference if they had chosen to use Persona. Too bad.
“To be honest, the number of login options is getting way out of hand. We would have much preferred if WordPress.com just adopted Facebook, Twitter, or Google+. Better yet, Mozilla’s Persona would have been a great choice, although it doesn’t yet support Outlook.com accounts (only Yahoo and Gmail).”