Few notice the “spotter car” from Manny Sousa’s repo company as it scours Massachusetts parking lots, looking for vehicles whose owners have defaulted on their loans. Sousa’s unmarked car is part of a technological revolution that goes well beyond the repossession business, transforming any industry that wants to check on the whereabouts of ordinary people.

An automated reader attached to the spotter car takes a picture of every license plate it passes and sends it to a company in Texas that already has more than 1.8 billion plate scans from vehicles across the country. These scans mean big money for Sousa — typically $200 to $400 every time the spotter finds a vehicle that’s stolen or in default — so he runs his spotter around the clock, typically adding 8,000 plate scans to the database in Texas each day.

Private companies were quietly and rapidly finding ways to profit from much larger databases with little public discussion. Digital Recognition Network, with the help of about 400 repossession companies across the United States, has increased the number of license scans in its database tenfold since September 2010 and the firm continues to add another 70 million scans per month, according to company disclosures.

Digital Recognition’s top rival, Illinois-based MVTRAC, has not disclosed the size of its database, but claimed in a 2012 Wall Street Journal interview to have scans of “a large majority” of vehicles registered in the United States. […]