Giddy policemen are not a good thing.

Via Wendy McElroy:

This headline from the Florida Sun-Sentinel (03/26): New cameras in police cruisers can analyze thousands of license tags a day. The article opens, The multi-camera and scanner system, mounted on the trunk, hood, or roof of a cruiser, takes pictures as the officer drives through the city looking for stolen vehicles and criminals. The camera is capable of snooping through as many as 10,000 license plates a shift, leaving officials a bit giddy about its effectiveness.
...
...quietly protect your privacy by making your plates more difficult to scan. Dirt is good but many areas have laws against driving with obscured plates. I cannot recommend the product because I have not used it but Phantom Plate promises to make your license plate unreadable by a scanner without obscuring it to the naked eye.

I haven't used it either - and of course have no use for it here - but it does sound like something you might want to check out if you live in a place where such things are a concern. Just FYI.