I agree that the principle is interesting. The music/video industry asserts that you're not allowed to play/show some media item that you've bought. Amazon do

I agree that the principle is interesting. The music/video industry asserts that you're not allowed to play/show some media item that you've bought. Amazon doesn't allow you to resell or bequeath Kindle books. Caterpillar doesn't let you repair your own tractor. The first sale doctrine was established in a very different time.