POSTSCRIPT: I can't verify the veracity of the following, but yesterday I received a mass emailing from a good friend explaining how street gangs are 'tagging' cars in parking lots at gun stores, shooting ranges and gun shows. Then when the automobile, after tagging, is driven to another part of the area and left empty it is broken into and the weapons and gear stolen.
Supposedly, a number of expensive shotguns were stolen from vehicles this past summer at an event held near San Antonio, Texas and law enforcement feels this was the technique that identified the vehicles in each case. It also appears the same technique was used recently in Denver, Colorado.
A small adhesive dot is place on the bumper or the license plate to 'mark' the vehicle, when empty, as a target for thieves specializing in weapons theft.
So be aware and watch for anything 'strange' being put on your vehicle whenever you leave a 'Fun-Show' or shooting range...
Thanks to Farmer Frank for the warning. Hadn't heard of this before, but it doesn't surprise me.