I should mention I found one site that takes that little guide seriously. I'm not posting it as it might provoke every flame war ever dreamed of in this one thread.

Now, about filing. Mary, I beg to differ with you about being either a horizontal or vertical filer. I do both. The piles are vertical. When they tip over, they're horizontal. I guess I believe that the vertical bits look neater, but it's easier to find stuff filed horizontally. Oh well - as long as I can walk past them it doesn't really matter too much.