So rather than coasting to the shoulder when you run out of gas your tires immediately slam full on coming to a screeching, uncontrolled stop in the middle of the highway?
hah. I didn't see this before I wrote my comment. Really makes you wonder about this common SWE fantasy of mew ways to turn cars into big electronic touch screen devices, whether the people dreaming these ideas up have ever actually driven a car.
Nope. If your car lost power for whatever reason, the system would scavenge power from the inertia of the car and the brakes would still operate as they do when the car is operating nominally. The 1-10w needed to run the braking system is a rounding error in comparison to the 4-10kW of wind/rolling resistance at freeway speeds.