That's why whenever I buy a DRM-ed content like a book on my Kindle, I always download an un-DRM-ed copy from Librusec. If it's unavailable, I un-DRM it myself. This is for non-fiction where I'm likely to go back and read the book (or, more likely, its fragments) again, possibly many times. For fiction, I don't care that much - usually I read a fiction book once in a lifetime so if Amazon steals it from me or not it makes no difference. It's not like I can give it to someone like with a physical book.