I worked with a guy who had the messiest desk. Complete disaster of books, cables, disk drives, tons of random geek toys, and whatever other detritus landed on it. But he knew where each and every thing was. If you touched anything he would notice and get very unhappy.

Our boss was a neat and tidy sort who kept his desk completely spotless. Nothing on it but a laptop. One day he came up and said "You know they say that a cluttered desk is a sign of a cluttered mind."

Ben didn't miss a beat and asked "Well Rob, if that's true, what is an empty desk a sign of?"