Hall of bad ideas (via Bruce Schneier):

OnStar will soon include the ability for the police to shut off your engine remotely. Buses are getting the same capability, in case terrorists want to re-enact the movie Speed. The Pentagon wants a kill switch installed on airplanes, and is worried about potential enemies installing kill switches on their own equipment.

Yeah, that's what I want: open season for hackers to break into "secure" systems and shut them down just for fun. I'm not sure you could come up with a worse idea if you worked at it. This is like DRM, but with extra stupidity added in.