At first, the idea of a federal-level requirement for electronic “black boxes” for your cars sounds a bit Big Brother-ish. But in fact, many cars already include such devices, and there is confusion resulting from different data recording methods, law enforcement needs, and so on. Some may see a slippery slope ending in dash cameras and GPS logging, but others see the potential for vastly increased safety and standardized legal limits for that kind of data.
Wired considers the question in depth here – but whatever the benefits, this is guaranteed to be a controversial subject.