Charlie Stross tries to scare us with terrorist schemes:
It should be relatively easy to ride a bus around a capital city and identify the GPS coordinates of, for example, the American embassy or important government offices. Then, with the aid of a PDA, some software, and a digital to analog converter, it is possible to build a GPS-detonated suitcase bomb — a bomb which will go off when it comes within a pre-set blast radius of the target, rather than at a pre-set time. There’s no reason for the terrorist who planted it to hang around in the same country once it’s on the bus. Or to actively send it a detonation command. It’s entirely passive, highly accurate, cheap to build — plant a dozen of these on busses and you have all the makings of another Madrid atrocity. Should we therefore block GPS signals in cities?
We need a public debate on this, and we need it now, because the future is wireless, and as we’re discovering wireless technologies massively lower the barrier to causing havoc.