In 2002, Microsoft security researcher Peter Biddle (previously) published The Darknet and the Future of Content Distribution, a paper that argued that DRM would always fail and that traditional forms of censorship would be harder and harder to execute online (it also coined the term "Darknet"); today, in honor of America's mass freakout over 3D printed guns, he's published an updated version, which mostly consists of adding "this applies to guns, too" over and over again, for people who are unclear on the concept.
UPDATE: Because some people seem to have missed out on the importance of this: ANY PHYSICAL OBJECT THAT CAN BE REPRESENTED AND DISTRIBUTED AS DIGITAL DATA SHOULD BE CONSIDERED A FULL BENEFICIARY OF THE CONCLUSIONS OF THIS PAPER. 3D PRINTED GUNS START OUT AS DATA . They are then rendered (which is to say, made usable in the analog universe) in a 3D printer. They are no different from music, books or movies. If you want to freak out about things that still haven’t quite happened yet imagine the future of CRISPR and drug recombination, which is also just digital information that is rendered through a “printer”. Add nano-explosives, autonomous drones, diseases, bacteria, viruses, DNA, “fake news” and porn face swapping. Anything that can be data will be darknetted.