License plates are typically captured from cameras mounted on police cars or bridges. Originally, the images were only used for law enforcement purposes (for example, to identify a stolen car). However, the American Civil Liberties Union (ACLU) looked over 26,000 police documents which revealed that the captured images of license plates, many of which belonging to innocent drivers, are being stored in a database. The images are held anywhere from 48 hours to 5 or more years depending on the state.
Why should we be concerned? Catherine Crump from ACLU explains it clearly.”What can location data reveal about people? Trips to places of worship, political protests, or gun ranges can be powerful indicators of people’s beliefs. Is it really the government’s business how often you go to the drug store or liquor store, what doctors you visit, and the identities of your friends?”
For more information, check out these fantastic slides created by ACLU that explains the technology in more detail.