You forgot illegal; it is illegal to steal IP just as it is illegal to steal physical property. http://www.uspto.gov/about/ipm/industries_in_focus.jsp
According the US Patent and Trademark Office IP (Intellectual Property) supports 35% of the U.S. GDP, 40 million jobs, and contributes $5T to the economy yearly. The theft of patents, software, music, movies, books and other forms of IP erodes the U.S. economy while strengthening the economy of countries that steal IP. China is a prime example.
IP intensive US industries accounted for 19% of U.S. exports in 2007 and are the fastest growing industrial sector.