That's a good point. To delegate your sign-up/log-in to a third party, you have to put some degree of trust into that service provider. The numbers show that most people "trust" Facebook, Google and others enough to do so.

The idea of removing the need for trust is elegant and some of the technical folks do appreciate it. However, it's difficult to communicate that to the wider audience, especially since it is not really aware of there being an issue with that.

Firefox Accounts is a step into the right direction regarding this, so let's see how this goes.