That's like saying someone threw a rock at you and because you didn't look around before it hit you, its your fault.
The cheating is the problem, not the fact that people are ignorant about it.
http://rockyroadblog.com/caveat-emptor-vetting-mpg-claims-30...
The same transaction costs argument for regulatory disclosure apply to the quality of such disclosure as well. Ever try reading nutritional labels? It goes on and on...has very little to do with one particular instance.
That being said, a auto is a capital good and a substantial purchase and investing some time to understand the buying process is both economic and sensible. so in this case the faux shock/outrage seems particularly misplaced...as the arguments for ignorance are weak indeed.