We have them here, but they are only used when the booted vehicle's plate has been run, and it comes back that the vehicle has five or more unpaid parking tickets. It does get the owner's attention. The local police (and civilian employees of the police department) are the only ones authorized to boot a vehicle.
On the other side, there was a towing service that ran a scam near a major league ball park. The owner's wife and her brother had a "Parking $10" sign printed up, and covered up a "No Parking On This Lot" sign. They could get about 20 cars on the small lot, then pull down their sign, and the towing service owner would bring his truck, an haul the cars away, then charge the owners between $200 and $400 to get them back.
The three of them got caught when one of the victims of the scam parked a block or so away, and took a nice set of photos with a digital camera equipped with a 500 millimeter telephoto lens. He sued the shit out of the scammers, won the case with punitive damages awarded, and the pics were turned over to the local district attorney for a criminal prosecution.
The scammers went to jail. Got five year sentences, four years suspended. He, his wife, and her brother were stripped of everything they owned, save for their primary residences and appliances (stove and refrigerator) and two cars. His towing business and four tow trucks were sold at auction to pay back the people he had scammed.
(Gawd, I love a story with a happy ending.)
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