Assigning some bytes to a person is easy, but how do you authorize transactions? People will not keep a secret... secret. People will not remember a secret.

Assigning some bytes to a person is easy, but how do you authorize transactions? People will not keep a secret... secret. People will not remember a secret. People will lose cards. Smart phone adoption is maybe 75% in the US. Many people do not have internet access, a phone line, or even electricity! People have all sorts of disabilities, many can't read, and many still don't have permanent housing or even an address. The technology is the easy part.