My friend had a nice stereo in an older car. When asked why he wasn't worried about his car being broken into (or even why he often didn't bother to lock his cars' doors) he told me about his security system which he swore was more powerful than any car alarm: filth.
Basically, by covering the interior of his car in garbage, and by stubbornly refusing to wash the exterior, his car looked so dirty that prowlers assumed that there was no way that the car contained anything of value.
He's clearly onto something. I suspect it might even be more than a good rationalization for not cleaning ones car.
