Earlier quoted context omitted.
We already use social security numbers for everything (insurance, credit, etc.). It's pretty much a national ID, just a shitty one.
The way they got SSNs through is by promising that it would be illegal to use them for identification. The only remnant of that is that it (still?) remains illegal to refuse services to people who refuse to give their social security numbers, although if you do it you'll break customer service.
I'd love to read this, for anyone more familiar with the legislation/where to find it.