Cars currently have black boxes in them, they're similar to what are required to be in airplanes. They record things like are the seat belts in use, did the airbags deploy, what was the seat position for the driver, were the anti-lock brakes in use, etc. The problem is that they aren't any requirements regarding what data points are logged prior to a collision nor for how long they are logged. They also require a factory expert to analyze the data.
They can be good, they can be bad. Good in that they can help reconstruct crashes and ultimately lead to safer vehicles, they can also theoretically help find you not guilty in an accident, they helped Toyota prove that it was pretty much idiot drivers causing phantom acceleration in the Prius, the notable exception was it confirmed a problem in the death of the police officer and his family in a Lexus in California. But there's a lot of paranoia of "Big Brother" boxes and Nannystate. I think these concerns are largely unfounded, I think it's more of a case of the NHTSA wanting more standardized data. Law enforcement has, in most cases, had the ability to subpoena the data from these boxes when they need it, that probably would not change. I don't know if insurance companies would have the right to this data, they might have to request it from the customer.
Most cars already have these in one form or another, it's usually described on the first page or two of the owner's manual. If your car has an air bag, it probably has a black box.
I think it's a good idea, we'll see what happens. There was a lot of hype about the announcement, I'm sure things will become clearer as the proposed regulation gets developed.
http://www.wired.com/autopia/2011/05/automotive-black-boxes/http://yro.slashdot.org/story/11/05/24/0159212/Mandatory-Automotive-Black-Boxes-May-Be-On-the-Way
