I think all of the states are trying to upgrade the state driver's licenses, i.e. make harder to counterfiet etc. In Calif. we also have to supply our SSN. I think the combination of SSN and state DL is going to be the standard for a national id at some point.
It sucks because the state miskeyed mine(reversing the 2 middle digits somehow), and it took me months to get it straighten out. The Calif. DMV verifies the name and SSN # against the Social Security Administration's name and number and everything had better match exactly or your're screwed. I used my middle initial in my SSN name, but my Calif DL had none, another trip to the Social Security office. So big brother is coming sooner than you think.
The main motivation for the SSN # was to track down deadbeat dads, or so that's what the Calif govt told the sheeple. For me, it is another way for the govt to track you. If they wanted to find your whole life story, just get your SSN and go to TRW etc, and your life is like an open book, if they really wanted to look.
For some of the folks, on this board that are a lot younger than I; SSN number was never a form of id and you could put any name your heart desires on it, at some point a fews ago, that philosophy changed.
WELCOME TO THE BRAVE NEW WORLD.