Illflem, that's exactly what happened to the top of the cab on my '95. A piece of paint about 12 by 18 inches sailed off at the car wash. Boy was I surprised! I had bought the truck used, and it had right about 98,000 miles on it. I had to have some bodywork done on the driver's door about 6 months later, and just paid the body shop $50 to paint and clearcoat the top. The bodyshop owner and I looked really carefully at the top, before repainting, and we couldn't see that any clearcoat at all had been applied there. The other parts of the truck all were clearcoated and have lasted fine.
After the paint delaminated, primered metal was what was left--a very clear case of paint failure, for the paint simply didn't adhere to the primer very well. It probably wasn't due to the clearcoat missing, it was probably due to EPA regulations making it harder and harder to produce good paints!