Speaking of GOG.com (story above), there's an interview on Ars Technica where GOG.com's managing director Guillaume Rambourg discusses the success they've had selling games with no digital rights management. Here's his example of their experience, which also touches on the success of their recently implemented money-back guarantee:

There is an even more recent research under way that seems to prove that dropping DRM in the music industry resulted in an up to 41 percent increase in sales. GOG.com's DRM-free, day-one release of The Witcher 2: Assassins of Kings, a AAA+ game by any standards, is a great case study. At release, the version widely available on torrent sites was not the DRM-free GOG version but the one that posed any sort of challenge to the hackers, the one that included DRM.

The game was downloaded illegally roughly 4.5 million times, but to use the industry-wide practice and treat those entirely as "lost sales" is a massive misunderstanding. Most pirates never had any intent to buy the game in the first place; some surely became paying customers after trying it out or when the title became available at a discounted price. To drive the point home, CDP Red won't be using any DRM for their upcoming release of The Witcher 3: The Wild Hunt. As Marcin Iwinski recently put it: "Will it be more pirated than if we put DRM on it? I definitely don't think so. [...] With a DRM-free release, we're hoping to build more trust between us and gamers."

Finally, in our own experience we've found that trusting users to treat us well pays off and that our DRM-free approach is certainly not costing us business. Two of the many examples that come to mind: we see an average number of downloads per game that's somewhere below two—which means that users aren't taking advantage of DRM-free gaming to share accounts around.

Another great example comes from our recent launch of our 30-day, money-back guarantee where, if a game bought on GOG.com ends up not working despite what we can do to help you, we'll refund you your money. While we've seen an uptick in customer support requests, it's in the realm of a 200 percent or 300 percent increase in queries that seem legitimate for the most part, not a titanic flood of people who want to try to find a way to scam GOG.com out of a free game. I believe that people, by and large, try to be good; treating them that way for five years at GOG.com seems to bear out our hypothesis.