Hide user section unless password protection is set
It's not uncommon for users to go to the password protection option, select a folder, fill out both the grey and the white sections, and then click "add/modify authorized user" button, thinking that they're saving both sections. I've done it myself when I'm in a hurry.
I would like to suggest that the bottom section allow users to be manipulated be hidden unless the directory is indeed password protected. This will force users to click "save" before they move on to the users section and eliminate some confusion.