Googling info..IT side think GPS issue is minor...Aviation/DoD/ side think there are major issues with freq band being so close...not just those 40000 land sites but two satellites covering all of the US by 2015.
Funnily enough, both sides think the FCC is their friend.
EDIT to add. lightsquared are/have been accumulating bandwidth for the last eight years...this last bit is AFTER they have flown their birds into space and now they want to get a licence from the FCC?