Users Set the Parent Menu Item to "Add a main menu item"

criticality: 
Moderate
Drupal7: 
Open

Some users when creating a menu item (either from the node form or in the Menu administration pages) will select the default "Add a main menu item" item from the list of menu items.

Implications: 

Without the menu items at all, users also get confused about where the "Main menu" and "Secondary menu" exist.

http://drupal.org/node/302149 - original issue where these links were added.

Solution: 
The "Add a main menu item" item should not be a real menu item. Instead it should be added through the theme layer when the menu is being displayed and the menu is empty.