This can be done in a decentralized manner where people host their identity. For example, for email you can buy a domain name and set the DNS MX record to point to whichever email server you want to receive email at. For identity you could have a DNS record with a public key, and then use your private key to generate random signed identities for every website. Obviously that's a bit out of reach of normal people, but it can be implimented without too much complexity. And inevitably it'll get pretty centralized for 90% of people, just like 90% of people use a @gmail.com email address, but the option will still be there for those who need it.
- SSN is great and works well for everything.
It turns out that you can completely centralize ID and authentication, provided you have a government which is mercilessly willing to violate your privacy...
It's a very US-Centric view of the world.
- The inconsistent, chaotic patchwork of ID systems is more resilient than a monoculture, and definitely more resilient than a centralized solution.
- The gaps provide necessary cover for people who need to hide.
- Doubt usually plays in the little guy's favor. The bank eats the loss when it can't prove the debt is yours. Copyright lawsuit fails when it could have been anyone at that IP address.
- The difficulty of strong ID verification is what keeps it from being used gratuitously. A PKI or SSO provider that's too good will soon be required for every little thing.
- Customer identity is something a business should own, not rent.