Bruce Perens tells us that patents impede innovation his article, The Monster Arrives: Software Patent Lawsuits Against Open Source Developers:
Patents were created as a means to get inventors to disclose their inventions, rather than keep them secret. The disclosure of an invention was supposed to allow others to more easily build on that invention, thus creating more inventions. But the patent system has evolved into something useless for the purpose of disclosure, and engineers are now instructed to avoid looking at other companies’ patents because if the victim of a patent lawsuit can be shown to have known of a patent, the award to the patent holder is tripled. There have been no reliable studies that show software patenting to have encouraged innovation, and there is much evidence that they actually impede it.