Ars Technica reports on a study that found "[under certain conditions] eliminating DRM restrictions can lead to an increase in sales of legal downloads, a decrease in sales of traditional CDs, and a decrease in piracy"
"This is in stark contrast to the view that removing DRM will unconditionally increase the level of piracy.""
A game we all win: Dumping DRM can increase sales while reducing piracy
The research report is also available:
Music Downloads and the Flip Side of Digital Rights Management Protection.