> Replace the single human-memorable token (SSN) with a unique public/private key pair

There are governments that work on solutions to give each citizen a certificate. What I would love to see would be the possibility to issue your own sub-identities that only exhibit as much information as you want/need to share for that specific use case. E.g. if you need to make $20k/yr for a new mobile phone plan, you can issue an identity that makes $20k/yr as long as you make at least that.