Like say an all-clad all-stainless exterior pan?
I could see enamel-coated getting etched or banged up on enamel coated cast iron. Obviously things like carbon steel and cast iron shouldn't go in dishwashers.
How do stainless and nonstick get damaged in the dishwasher short of getting banged up when hitting other items? I also hear this about knives. I have stainless wustof knives, and while I never put them in the dishwasher (too easy to clean by hand and I can't guarantee they won't hit stuff), is the only reason not to put stainless knives in the dishwasher besides the possibility of dulling the edge due to mechanical damage?