There are many different proof-of-human mechanisms that you can layer on top of each other. They have different and hence complementary failure modes.Use as many as you can cheaply introduce. From 2FA to MFA, multi-factor authentication.Steven Sinofsky (@stevesi):@balajis How do you solve the realID and association with an account problem (in case authentication is breached)? Or does this depend on algorithmic determination of bot'ness? ...