It sounded to me like GGP was interested in hearing about any SSN that was assumed to be public knowledge, and Russia's was just the igniting spark for the question. GP makes it clear that, yes, there exists an example where the SSN is a public identifier.

GGP:

> Are their identification codes used as a shitty master password to their life too? I'd love to get to a system where your tax id was assumed to public knowledge