In my testing I found that if you create a course (in my case I copied a course) and then delete one of the courses, if there is any media that is "shared" between courses, like an introduction or something, It will deleted the shared media from all the courses.
This poses a HUGE problem if for some reason you are cleaning up your courses.
I luckily don't allow my teachers to delete courses, but if someone did this in admin it would delete the teachers content that is shared.
This needs to be revisited most definitely. Maybe put a check in place to see if it's used in multiple courses and give the person deleting the course the option to say yes or no to deleting the shared media.