[the_gipsy]

In Spain each person has a unique ID number assigned at birth. The numbers for newborns are geographically pre-distributed to guarantee uniqueness despite delay in paperwork. It is universally accepted that this ID "number" (it actually has one letter too) is all you need to identify yourself, ever.

Except that I knew a coworker who had a duplicate ID. An extremely rare event, they messed up the pre-assignment and there is another dude somewhere with his same ID. So from time to time, some system would tell him that his ID was already registered. A lot of banks and stuff like private healthcare systems like to use the DNI as usernames.

He tried to get his ID changed, but that was such a foreign concept to any of the involved institutions, that he had to give up because there simply is no such procedure. I guess he could have taken it to court, but the guy decided to just live with it (the justice system is quite slow here).

[Cthulhu_]

The fact that it's fixed / can never be changed is a massive problem with social security numbers. That, and the fact it's often used as authentication instead of identification. They're moving away from that slowly, but it's taking a lot of time and effort.

[skeletal88]

The problem with ssn is specific to the US. Other countries have sane ways of authenticating citizens and the personal id number is just used as a global foreign kes for all government or public or bank database where you need to uniquely identify a citizen.