It doesn't require any of these things. I have been using mine for ~6 months without a credit card. I have downloaded a number of free applications and the onl

It doesn't require any of these things. I have been using mine for ~6 months without a credit card. I have downloaded a number of free applications and the only times I had to log in was when I decided to rate them. I have not tested non-free applications, but the documentation seems to indicate that you have the choice between PayPal or some operator-provided billing mechanism. I don't know the details, though. You do not have a system-wide identity. The Marketplace supports authentication through Mozilla Persona/BrowserID, which is quite different from other single sign-on authentication schemes, insofar as it is anonymous, almost zero-knowledge, open-source and decentralized (admittedly, I don't know of any Persona provider other than Mozilla, but anyone with a http server can become a Persona provider).