http://www.msnbc.msn.com/id/6720387/
"President Bush has ordered plans for temporarily disabling the U.S. network of global positioning satellites during a national crisis to prevent terrorists from using the navigational technology,"
"The GPS system is vital to commercial aviation and marine shipping."
"The U.S. network comprises more than two dozen satellites that act as beacons, sending location-specific radio signals that are recognized by devices popular with motorists, hikers, pilots and sailors."
Wait a few more years until GPS becomes critical, and sit back while someone launches an attack expecting GPS to be shut down. Pretty convenient, huh?