Digital Rights Management (DRM) is one of the thorniest issues in the the Digital Media world. Views on the subject range from the libertarian perspective that all digital content represents knowledge and should therefore be "free"; to the stance of the major media giants, who claim that digital media represents intellectual property that should be copyrighted in the same way that print media is copyrighted; and enforced accordingly (in all honesty, a much more realistic approach).
Follow this link for an Overview of Digital Rights Management.
Some level of DRM is usually necessary to deter piracy, even if it is impossible to completely eliminate unauthorized duplication of content. The trick is to get the level of content accessibility just right. Too little, your content will be easily duplicated and distributed on the black market. Too much, and you may alienate the legitimate users by imposing too many restrictions.
For example, the Electronic Frontier foundation contends that DRM does little to deter content piracy, but often does prevent legitimate content users from making backups, or transferring their content from one format to another. Read their article on the subject here.
A more extreme position is taken by DefectiveByDesign.org which describes itself as "a broad-based anti-DRM campaign that is targeting Big Media, unhelpful manufacturers and DRM distributors". Their goal appears to be no less than the complete elimination of all DRM restrictions' in effect the position that all digital content should be "free", despite the effort that went into the creation of that content.