> - That a person cannot own more than one of.

Exactly one seems hard to implement (some kind of global registry?). I think relaxing this requirement slightly, such that a user could for instance get a small number of different identities by going to different attestors, would be easier to implement while also making for a better balance. That is, I don't want users to be able to trivially make thousands of accounts, but I also don't want websites to be able to entirely prevent privacy throwaway accounts, for a false ban from Google's services to be bound to your soul for life, to be permanently locked out using anything digital because your identifier was compromised by malware and can't be "reset", or so on.