Comment 4 for bug 563226

TC, this would be a major design change, and it is not based on existing design. Thus, it is not a papercut, but you are welcome to bring it up on a mailing list. ( eg: GNOME's Nautilus list: http://mail.gnome.org/mailman/listinfo/nautilus-list ).

Note that Ctrl+W is the shortcut for File›Close in Nautilus's main menu. You can see that by opening the File menu and looking to the right side. This is the same for every single File menu; great cares are taken to keep these shortcuts the same.
The idea is that people will probably learn the shortcuts by looking at the menus first, and it helps them that we consistently use the same key combinations for the same operations as they are visually described in the menus. By having some odd case where File›Close has Ctrl+Q, we are undermining that.

There may be a case for having Ctrl+Q as a hidden shortcut that does the same thing, but it could create false assumptions so should be discussed in the appropriate forums first.

Also, Firefox doesn't behave that way. Pressing Ctrl+Q tells Firefox to quit, closing all windows. Pressing Ctrl+W closes the current window, and the Firefox process may decide to stop as well if it is no longer being useful. Ctrl+W should always be equivalent, for casual end users, to pressing Alt+F4.