We decided to use Facebook and Bitcoin because we think they have the largest prospective markets for growth. Any and all identity/authentication providers are

We decided to use Facebook and Bitcoin because we think they have the largest prospective markets for growth. Any and all identity/authentication providers are being discussed, including SMS, Email, TOPT clients like Google Authenticator, and OAuth from any provider. We are also discussing alternate blockchains. We cannot promise anything at this time as our strategies as a company may change but I will say that we could very easily change a few settings to support these other identities and blockchains.