Few books are sold without DRM protection. I recommend to remove DRM from all legally purchased books for backing them up and reading them on any devices. Although Kindle Store and Barnes & Noble look like growing and that they will never leave the arena, you never know what will happen. Just read what has happened to users of Napster and MTV Urge music services to learn why not to trust even big names. Plus it is always good to be able to use any book reader, not the best one that Amazon or B&N can offer (although currently both Kindle and Nook 2 are probabaly the best readers).