The right way to do it is to make it pretty obvious. Kind of like text-area enhancement with a slider and status bar at the bottom at the bottom with the words

The right way to do it is to make it pretty obvious. Kind of like text-area enhancement with a slider and status bar at the bottom at the bottom with the words 'Auto Save: On', that the user can toggle. The truly paranoid will write stuff in a text editor and paste it in, the less paranoid will turn it off. But I have a feeling most people will leave it on.