Just think of a text file that contains passwords. (Not advisable, but some people might do it) Porn folder. (I guess many people have it lying around somewhere) Bills, secret letters, ...

Think of anything you have on your hard disk, but which you don't really want to pop up in "recently used" if you lend your laptop for a few minutes to a random person for mail checking.

IMHO Gnome needs support to hide folders/files from those obvious places, and with that I mean an "average joe"-compatible setting in either the folder properties dialog or a System > Privacy kind of GUI management thing - *not* a hidden arcane config file or gnome tweak tool setting the average user can never handle and make use of.

With the search, recently used dialogs and whatever popping all over, I think it is about time that someone puts some thoughts into this.

As an easy/fast solution I'd suggest a file/folder flag (accessible through nautilus file/folder properties, e.g. "Hide this file/folder from Recently used and Search dialogs") that doesn't really hide the folder from normal browse but omits it from all the recently used/search/zeitgeist/tag generation/whatever fancy things.