I have never understood why the menus in Mac OS X (Snow Leopard or Lion) allow the user to click-through them, which closes the menu with nothing selected. For example, if I were to click on the gray bar of a drop-down menu, as in XCode’s menu:

then it will close the menu with nothing selected. I think all interaction designs utilizing menus should keep the menu open when the user clicks inside the menu, but not on a selection. This makes the most sense to me, obviously with no data to back it up in this post. Maybe I’ll make a demo to test it out at a later date to gather some feedback from people. 

If anyone knows the history of this design decision in OS menus and elsewhere, please let me know.