I always found the "Nobody" list permission confusing (why would someone create a list and not let anybody, including themselves, change the contents?). I have learned since that it was meant as a way to make the list "read only" after you've added contents to it. I know I'm not the only one confused by this. I wonder if it'd be easier to understand if it was a checkbox labeled "Read only", "Locked" or "Lock list" (similar to locking a budget in acquisitions).