Well see the thing is, and I am going to argue this from a completely legal perspective, if no one could drive OVER the speed limit, no one would have to pass anyone going AT the speed limit. I recall from my Drivers Ed years ago that passing a car in a passing zone was only legal if you didn't have to break the posted speed limit to accomplish the pass. If the car you are passing is going the speed limit you have NO legal reason to need to pass that vehicle. If the car is traveling enough below the speed limit to pass them without breaking the speed limit for a long enough period for the proposed limiter to kick in and reduce your speed to the posted limit.
All that being said I think that speed limits are posted much lower than they need to be. But we do have to take into account that driving a car is not a right, and as such if you don't follow the rules put forth by governments you deserve to lose the your ability to drive.