"It's in the nature of patents that they give a monopoly to whoever holds them for 20 years. James Watt patented various vital aspects of the steam engine. Yet, you look at steam engine development and nothing happened for 20 years during the life of the Watt's patent. When that patent lapsed, there was a great flaring of steam engine innovation and then the industrial evolution. ~ Adrian Bowyer (RapRap)"
Fabricated: The New World of 3D Printing, p. 231