Patent thickets are good- they prevent innovation and diffusion of harmful inventions

Second, in an indirect way, the patent system can reduce negative externalities by constraining the dissemination of harmful or undesirable inventions. While patents aim to promote invention, observers have long recognized that too much patent protection can have the opposite effect.145 Innovations are often subject to multiple, overlapping patents, and the need to clear all of these exclusive rights may be prohibitively expensive. Scholars have extensively explored the innovation-dampening effects of so-called "anticommons" and "patent thickets."146 In a provocative article, Professors Chris Cotropia and Jim Gibson argue that the ability of patents to inhibit innovation can have some unexpected benefits.147 In particular, patents can impede innovation and dissemination of technologies in harmful industries. As a descriptive matter, however, several of the industries that Cotropia and Gibson examine, such as biotechnology, seem to be thriving quite well with robust patent protection. Additionally, as a normative matter, it is far from clear that industries like biotechnology are ones that we would want to suppress, a point that the authors recognize.148 Cotropia and Gibson offer a valuable insight that policymakers can use patents o restrain innovation in undesirable areas. However, as presently constituted, the patent system does not do much in this regard in any targeted fashion.