From “The Big DRM Mistake?“:
Fundamentally, DRM is a about persistent access control – it is a term for a set of technologies that allow for data to be protected beyond the file system of the original machine. Thus, for example, the read/write/execute access control on most *nix file systems will not only be applicable to the original machine but to all machines.
Stated in these terms, I agree with the aims of DRM. However, it is the ways in which large media and software businesses have mis-applied DRM that have ruined the associations most users have with the technology.