rotor if not treated in a timely manner. If you have a failed caliper, it is either not releasing after the breke pedal is released causing rotor damage or is frozen, not apply preassure when the brake is pressed. In either case the car will drag one way or another when braking and can be compensated for. If one is aware of the issue and doesnt have a tendance to stomp the brake pedal, he sould be fine.
thanx,
bill