First thought, I can fly up at maximum rate to a toll booth line, or line of traffic at a red traffic light, and the car will stop me without collision in dry conditions? That'll be TERRIFYING to the car in line. That'll mean MORE accidents for those accustomed to such systems in the wet or snow.
(It's like antilock brakes, they increase the stopping distance for those who properly apply brakes, but reduce it for those that don't, but nowadays everyone has to adapt to a different technique that is a greater stopping distance.)
Second thought, I can push a button to keep the guy next to me from going anywhere because his brakes are now activated? I can get the guy on the highway who is a jerk to suddenly be stopped by using an app on my phone? The hacking potential is awesome!
Third thought, now if you drive over the speed limit, your car will brake wherever people decide you shouldn't be going faster than some amount, regardless of reasons for doing so, or your brakes will be worn down and overheated. Great.
Rush's "Red Barchetta" song is no longer the future, it's hear.
PS: Just like it has come time to stop updating Windows to prevent MS from installing malware via updates, it might be time to stop buying new cars.