John I can see your point regarding when your not shooitng competition. If you got the 36mp at your disposal why not use it. Cropping doesnt interest me so much as I am shooting at the other end of the scale with big subjects and ultra wide (weitwinkel) angle. Cropping a shot taken at 10mm on a Dx camera takes away the whole affect i am trying to achieve.
My opinion if old mate was waiting patiently infront of the Jawfishes hole with their 105mm and 12mp camera and captured a great jawfish shot filling the frame and with no need to crop shows me more skill than someone with a 60mm and D800 shooting further away and cropping the hell out of the image.
I think having competitions which allow no cropping or only very minor cropping makes in more competitive and shows increased skills need to achieve images. It might be "gone with the wind" to someone to have skills in being able to compose and frame a shot but its those with those skills which truely make successful photographers in any format which they choose to use. Isnt it the basics in photography to be able to compose your shot before you take that shot?
If heavy cropping were to be allowed its definately an unfair advantage to people that have 36mp Nikon D800 especailly in the field of macro photography when compared to 12-16mp cameras everyone else is using?