While there are no end to studies that attempt to justify whether a messy desk is good or bad for productivity, I remember one article I read a long time ago that rang true with me. The gist of it was that, in general (and there definitely are exceptions), but in general, the people with a messy desk in a typical office are the people who do most of the work and get things done. Thinking back to offices I have worked in, this has truth to it.
The "heart and soul" of the office, the people getting things done are usually those who you can't actually see the surface of their desk.
Then on the other hand, you have those guys with the bookcase with 3 binders on it and a desk with only a laptop, maybe a piece of paper or two, and a family photo in an expensive frame. And almost all the time, I'm never sure what these guys do, or in fact, what they are supposed to be doing.
If I need to get something done, my experience is that I would much rather go to the person with the messy desk vs. the person with the empty desk.
Of course, I'm sure you could find umpteen studies that disprove the above 
Printer-friendly view of this topic
