Quite often, when pasting in the script, node or graph editor, for whatever reason, Maya will paste the whole scene into itself, or whatever nodes are in the clip board (maybe the mouse curser had drifted out of the window I was using).
I guess it might be hard to prevent this from happening, but can it at least be undooable?
Animators are constantly accidentally pasting objects into the scene when they wanted to paste animation (it is easily done).