Digital rights management (DRM) is designed to prevent eBook customers from using digital technology beyond what a bookseller or mobile device manufacturer intended. It also protects from piracy the considerable investment of time and money that both authors and publishers invest in a new book.
While DRM protects the publisher, author and bookseller, it has drawbacks for the customer such as preventing them from moving books from device to device. A great example of this situation is how eBooks bought from Amazon cannot be downloaded on Barnes and Noble’s Nook reader. However there are more customer-friendly alternatives to DRM. See the full article from Good eReader here.