Many of us have encountered the problem where, by inadvertently applying a "no copy" texture to an object we're building, we suddenly find that we don't have permission to copy the object.
If you try to make a copy by shift-dragging one of the arrows while editing, you get an alert saying you don't have copy permission. Which is helpful.
However, if you try to do a "Save Object Back into My Inventory" using the Tools menu, the operation will fail silently. I think this should generate a warning message if you don't have the necessary permissions.
What would also be nice would be a warning whenever you applied a "no copy" texture, sound, or script to an object, alerting you to the fact that you're going to lose copy permission on the entire object by doing so.