|DRM is like a key-less padlock from Flickr (CC)|
However, it is illegal to do so for all DRM protected books.
What does this mean for you?
Publishers use third party software to handle the DRM-locks on your books. If that software or server goes " dark" (shuts down) then the ebooks are gone too, like with Fictionwise ebooks protected by Overdrive software. You keep paper books for years, don't you expect ebooks to do the same?
Interestingly, O'Reilly publishing discovered that sales of their textbooks more than doubled since they dropped DRM books 18+ months ago
Cory Doctorow's view: A Whip to beat us with
Ebook DRM provider goes dark, the books you paid for disappear