DRM (or Digital Rights Management) refers to the encryption that is often applied to electronic media to prevent customers from sharing the files they've purchased, or to keep them from using the files on any but the particular device that the seller wants them to use. The principle is the same, whether it's DRM-restrictions on a music file, a movie DVD, or an ebook. The purported purpose is to protect the copyright—to prevent the purchaser from engaging in misuse of the file, whether it's uploading it to a pirate site or sharing it with Grandma.
The effect of DRM is to alienate the customers, by limiting their fair use of the media, by making it hard to archive their purchases for safekeeping, and by generally getting in their way and treating them like would-be criminals. That's my view, and I believe that many of my fellow writers share it.
I've come to hate DRM, both as an author hoping to reach readers, and as a customer of books or music or movies hoping to use my purchases in the way that best suits my legitimate purposes. Therefore, whenever I have the choice, my ebooks will be available for purchase or download DRM-free.*
* I published The Kinshield Legacy for the Kindle without fully understanding what DRM was. Unfortunately, this cannot be changed once the book is published. Check out my pledge:
If you buy one of my ebooks from a store that uses DRM, and you can't download or read the book on your chosen device—whether it's the reader you originally bought it for or another—I want to help. Email me, preferably with some evidence of your purchase, and I will provide you with a copy that works for you. If you want to share it with a family member or a close friend the way you might a paper book, that's fine with me. If you want to convert the file to work on a different device, feel free. I trust you not to share it indiscriminately. I figure if I treat you with respect, you'll respect my need to earn a living, so I can continue to write. And you'll get to read my book and own a copy of it, which was the whole point to begin with.
adapted with permission from Jeffrey A. Carver