ABMW, The scenario you are trying to avoid (stopping when the car is accelerating uncontrollably) is due to the Lexus/Toyota driver side mat. What happens is that if you purchase a non-standard mat or stack two of them on the driver side (of certain Lexus/Toyota car), it is possible for the mat to skid forward over the gas pedal and push the pedal down, creating the unfortunate effect that you described. This has never happened to a BMW and in fact I have tried very hard to replicate it on my x5 and it won't happen. So, I believe you are safe there thanks to BMW's safety record. But I can't blame you for wanting to be absolutely sure about this. I personally am more worried about a bottle of water rolling under the brake pedal and causing the opposite effect.