Why, exactly, is the idea of an ID a threat to constitutional rights? Theoretically, you don't have to give out your SSA number, IF (1) You don't want to have a credit card; (2) don't want to be compensated for your work, and (3) never apply for a bank loan. That's kind of unreal, isn't it?

Drivers' licenses are extremely easy to forge. If you want to do bad stuff in California, just make up an "Arkansas driver's license." It wouldn't even have to look much like the licenses they give out in Arkansas; it would only have to look official.

On the other hand, a system based on national ID'S would not make much sense unless money was appropriated to enforce it. When I was in Germany in the sixties, one had to show an ID even to get lodging for the night, and the Gastwirt had to report your whereabouts to the police. So, some clever individual decided to have a Fahndungswoche, where local police were asked to actually check the reported ID's and compare the names with a list of known criminal fugitives. Someone leaked the information in advance, and numerous persons disappeared into the Black Forest. Nobody much got arrested. Ha Ha.