When I put my self-published book, "Pro PR Tips," on the Kindle store last week, there was a little option to enable or disable digital rights management. This is a new choice, stealthily introduced last week right around the time I was putting my book on the store. But it’s not, Amazon says, a new feature.
Rather, an Amazon spokesperson says that publishing DRM-free books has always been the default for publishers using the Digital Text Platform, a site that allows independent authors and small publishers to put their own works up on the Kindle store. The DTP site lets people upload HTML, Word, text, or PDF files as well as mobi files, which the Kindle reads natively. The site converts uploaded files as needed to the mobi format, now with optional DRM if desired, and puts them in the Kindle store.
Larger publishers submit their books to Amazon already in mobi format, and they appear as copy-protected on the Kindle if the mobi file comes to Amazon already protected, or open if not. It appears that nearly all books from mainstream publishers are protected. To see if a book is unprotected, look for a line that says, "Simultaneous Device Usage: Unlimited" in the product details block on the Amazon page for a book.
Amazon Quietly Lets Publishers Remove DRM (Update: Or Quietly Adds DRM?)