A password as secure as my phone is not promising; T-Mobible was recently happy to reset my lost PIN by having me give the last four digits of any phone number I'd dialled in the last 23 hours. I don't really think it's as useful two-factor because the token is only as secure as another company's password system. (Aside from the problems that you have to have a Google Account and a smartphone.)

I looked into this recently when Dreamhost launched google-authenticator instead of two-factor auth. Disappointing.