One of the things I wish we could start bringing into the public domain are zero-knowledge proofs for biometric data. Basically it'd enable the situation where the person being ID'd gives permission to a third party to know whether they're over 18 or not, and the entity requiring ID gets a yes/no without ever knowing the actual age or identity of the person.
No solution can be perfect, there will always be ways around things like that. DRM was supposed to stop piracy but it had the opposite effect. You can argue implementation problems all day along but that's exactly ALWAYS the issue.
