[ken_railey]

The brake pedal actuates the master cylinder, which is connected hydraulically to the calipers. Even if stomping on the brakes triggered more throttle problems, they are still plenty strong enough to stop the wheels from turning.

[owenmarshall]

In a car with ABS and brake assist - standard features on new cars - software has the ability to completely override your input.

[angersock]

Ah, but what about anti-lock brake systems?

[dmm]

Anti-lock brake systems work by reducing hydraulic pressure at a wheel that is determined to be slipping. It doesn't affect how braking is activated.

[angersock]

A little black box regulates the applied pressure due to criteria X.

I submit to you that if X is buggy, the little black box may decide never to allow pressure to hit the brakes. This in turn prevents braking.