The idea of a car-board black box doesn't bother us, despite the obvious issues of data privacy and commentary on modern society. We are, however, offended by another aspect: aesthetics.
Just take a look at the most recent version from Gadget Universe. Would you really want to mount one of these things on your dash or in the rear window of your car? It's almost as bad as a dog with a bobbing head.
Sure, it's possible that your recorded evidence could come in handy after an accident. But what if you were at fault because your vision was blocked by this 18- by 6-inch monstrosity?