Quote Originally Posted by wordsofwonder
The rationale behind David's recommendation is to minimize the number of places that something isn't, in the event that you forget where it is. It seems to me like separating your files like you suggested doesn't contradict this principle, since there shouldn't ordinarily be any overlap between your file areas. So, to me, this doesn't seem any different in principle from having separate files at home and at the office.

That being said, and considering the additional factors Katherine mentioned, I'd agree that splitting your files this way makes a lot of sense.
So we have a very useful GTD filing rule of thumb:

Separate your files into main categories when there is no overlap between these categories. Within main categories use A-Z filing.