DRM takes the control of the content or device’s functionality away from the owner–forcing compliance with a company’s preferences through sheer brute force.  DRM treats you, the person who bought the content, as a de facto criminal.  You can’t use the content you legally and rightfully purchased or licensed in the way that is consistent with private property rights.  DRM is also crazy expensive to develop and maintain — so every time you buy a piece of content with DRM on it (say an Overdrive eAudioBook or an AAC music file from iTunes), part of that money is going toward the development of software that restricts your rights to use that very piece of content you just bought.  Just think how many more books we could buy for our libraries if we weren’t paying out the nose for companies to develop DRM to “protect” them from their rightful owners.