Some of you guy's & girl's have hit the nail on the head when it comes to a/c cleaners doing the cockpit.
As an ex cleaner I can tell you it is scary stuff in there and we did have one new guy who wishing to impress his supervisor took it upon himself to spray all the nice switchs and guages liberally with a mild cleaning fluid solution!
Coming out of the cockpit with a large and satisfied grin on his face he was met by an engineer who asked "what the bloody hell he had been doing" and upon receiving the answer promptly grounded the a/c for 24 hours!
Cleaning of cockpits should be a specialized job but I do agree pilots should clean up after themselves with regard to papers/food etc.
Just to add although I am an ex cleaner I was not the new guy I mentioned above.HONEST.