When I pull the empeg out of the dash, I usually just leave the hole. But when I park the car in a high-risk situation, I cover the hole with the Honda blank plate. Since all other stereo equipment is hidden in the trunk or under the factory grilles, it looks like the car has no stereo installed. Nothing to steal, not a target.

Hey, that's not a bad idea!
Erm...no, I guess it wouldn't work for me after all. I'm pretty sure it would look stupid when the two speakers built in my back shelf would get noticed.