A very good friend of mine worked on the line at New Venture Gear for awhile (specifically, he ran the "shaver"). Anyway, he was telling me one day about the inspection process for the park pawl on automatic transmissions. He said if a "bad" one got by your station, or you built a bad one, you could lose your job ON THE SPOT.
For anyone who has ever rebuilt an automatic transmission, you understand why you would NEVER EVER EVER want to rely on the park pawl to hold the vehicle without the parking brake. Of course, I see people do it all the time and it's rare for a car to come out of park. But like a wise man once said, you can drive a car with your feet, but that doesn't mean it's to be done!
Sorry if I got off topic a bit.
-Ryan