Home Organization: Why You Need to Say "No" to Miscellaneous Files by Bonnie Hillman Shay
A pile of paper clutter represents a collection of decisions not made. Similarly, having a file folder labeled "MISCELLANEOUS" is just a way of postponing decision making. The category becomes a catchall, kind of like a junk drawer in the kitchen. But unlike the kitchen drawer, the file is more likely to be out of sight and out of mind. You forget what's there and if you do look in the file, it's often large and you waste time trying to find what you want.
Be more specific with your folder names and you'll have a better functioning filing system. This applies to computer and email files, too!