It would be nice if tags/coordinates and other elements could be marked as "obtained from a trusted source". For example: In my home town I got some official geodata.
These elements would still be editable but there would be a short warning massage before you can change them. ("This element has been been obtained a trusted source! Are you sure you want to edit it?")
It would be good to know if such elements would be somewhat safer from accidental/mistaken edits.
You could add a source tag, which will tell other mappers about the source of the data. (Theoretically, it would also be possible for editors to consider known source values when they decide how to treat the object, but afaik no editor currently chooses to do so.)