If Lightspeed and 4G were not enough of a threat, along comes $30 GPS jammers and $500 GPS spoofers.
http://www.newscientist.com/article/dn20202-gps-chaos-how-a-30-box-can-jam-your-life.html?full=true
http://www.newscientist.com/article/dn20202-gps-chaos-how-a-30-box-can-jam-your-life.html?full=true