There was a guy on NPR recently (yes, I listen to NPR) touting his new book about the power of disorganization. He claimed that you would often find action items that needed doing while searching for lost stuff, and that effective people in organizations tended to have cluttered desks.
That said, their is definitely an upper limit to effective disorganization. I find that if I work very hard to file the easily filable homogenous stuff, and leave the heterogenous stuff a mess, it works pretty well.
I kept that stuff organized together and out of my general correspondence.
They didn't try that again.