Estonia’s vision allowing anyone in the world to start using its ID-cards: goo.gl/kXPL7b. Do you see value in this kind of cloud service: login by inserting ID-card and PIN1; upload a file; encrypt it with PIN2; share it by writing other’s ID Card code; other can decrypt it by entering his PIN2. So, no site or state or NSA can get this document and it would be safer than just a password-encryption as I would need to steal your ID-card also.
I guess the second important aspect is that the other person, who you share with, is a real person. He cannot be fake as to get this ID card you need to authentificate yourself with biometric information
