This is a good summary of the potential disruption of GPS.
I have not seen the arguments of why would the FCC accept such a risk. If you are aware of a good source, please post a link and a short summary.
LightSquared is a company with plans to build a nationwide 4G-LTE wireless broadband network utilizing spectrum allocated for Mobile Satellite Service. The base stations of the LightSquared network will transmit signals in a radio band immediately adjacent to the Global Positioning System (GPS) frequencies, which has caused a great deal of concern that GPS signals may be desensitized, resulting in jamming and other forms of interference that will affect the reliability and functionality of GPS equipment.
If the LightSquared network is deployed on this spectrum, it is very likely that all GPS signal-receiving equipment will suffer signal degradation ranging from mild to severe. In response to concerns voiced from the military, industry and others, the Federal Communications Commission mandated tests be conducted and any conflicts resolved before LightSquared can begin operations. At present, the Technical Working Group, comprised of LightSquared members of the U.S. GPS Industry Council and other affected GPS users, is conducting tests of various GPS equipment under different operating scenarios to determine the depth and breadth of potential signal degradation.
The commercial stakes are high. The downstream industries that rely on professional and high precision GPS technology for their own business operations would face serious disruption to their operations should interference occur, and U.S. leadership and innovation would suffer. Although recreational and military applications for GPS equipment are larger in terms of equipment sales volume, commercial applications generate a large share of economic benefits for society.
Continues at http://www.saveourgps.org/pdf/GPS-Report-June-22-2011.pdf