This is similar to the "Recently Used Folders/Files" list that computers often supply you with. But it focuses on directories that you seem to have had trouble finding before you finally opened them.
This list of directories would improve hard disk search programs dramatically by allowing them to
first search folders where the item is most like to be found. (Or lost.)
To assemble such a list of directories, the computer could monitor you from the background, and, when it notices you navigating, opening, and closing, several folders in a row, without actually doing anything to a file within them, the computer could mentally add the folder you eventually *do* use to its "Frequently Lost Folders" list, knowing that you, no matter how many times you've asserted that now you definitely know which folder that document is in and will never forget that ever again, are probably full of mouse balls.
Proposed Interface Improvements:
An "Add to Frequently Lost Folders" button on the address bar so you can manually add locations to the list;
Option to turn off automatic Lost Folder List Updating (to be implemented in Windows after about 8 more stupid versions);
Folders in the explorer or navigator are listed in red if they are frequently lost - this helps draw your attention to them and also lets you right-click and choose "Remove from Lost Folders List" -- but see the previous paragraph before you select this...