Carmel elaborated on his reasoning, pointing out that particularly with independent developers, DRM solutions invariably just result in a lot of money being delivered to a third party. Further, he says that anything that is perceived as even remotely cumbersome will be rejected by users, with people preferring a cracked version that doesn't force them to enter a 32 character serial number. He brings out a good point in that popularity plays a key in how effective DRM will be and vice versa if a game is popular, people will be able to find it pirated with ease, whereas if it is unpopular then restrictive DRM could inhibit sales. Carmel also was an advocate of digital distribution and even advised trying to avoid retail altogether.
Those are strong words aimed at independent and small developers. He's not alone, though, as many other well-known companies and people have come forward to oppose DRM, if only partially. Bethesda is one of those, who feels that DRM is too much trouble, even if its goal is a good one. Gabe Newell of Valve is clearly not opposed to it (as Steam is one of the most popular DRM-laden clients in the world), but claims that most DRM strategies are just dumb, and vouches for pure digital distribution.