Over at the afore-mentioned Picker MobBlog, Julie Cohen counters Fred von Lohmann's argument that the DMCA is a failure at fighting the "darknet," arguing, among other things, that it's effective for influencing the kinds of technologies engineers create and keeping open source out of the mainstream (Cohen: Brilliant Advocacy; Incomplete Analysis):

[It's] quite possible to conclude that, from the industry's perspective, the fact that the DMCA was put in place while the technologies were still in their infancy is a feature, not a bug. I read the statute as intended in part (by its industry advocates, not by Congress) to establish a set of engineering incentives for new products and services, as to which consumers have no settled expectations, and to marginalize the open source movement (at least in the consumer market) by erecting insuperable obstacles to the development of interoperable entertainment platforms. Again, I think it's way too early to opine confidently that the statute isn't working toward these ends.

Here, I think Julie points us in the right direction. The legal regulation of TPMs [DRM] continues to pay one very large dividend to rightsholders, regardless of the Darknet: anti-circumvention regulation constrains innovation and competition in the technology marketplace, thereby ensuring, in the words of one entertainment industry lawyer, a "well-mannered marketplace."

Thanks to the DMCA, content owners deploying content with TPMs enjoy an important new "exclusive right"—the right to demand that technology vendors enter a licensing arrangement before they can build a device that can access or copy the content in question.