Are automatic license plate readers a violation of privacy?
Technologically - "You ain't seen nothing yet" in regards to computer aided surveillance in the hands of law enforcement.
Take the modern day hand-held laser gun that the police must hold in hand by the side of the highway and connect it to a system with "Computer Vision" that captures a picture of ALL of the cars in the view of the camera and renders an individual speed measure upon the screen for the police officer to cheery pick his target. Don't bother slowing down. By the time you realize that your speed has been captured - it will be too late. Prepare to pay your speeding ticket.
The pervasive scanning done by the actual subject of the story at the link above - Automated License Plate Reader - is a matter of strict policy.
The same police car that could scan for a car that has a driver with outstanding warrants (a good thing) is the same platform that could be mounted in various places around a city or highway system and monitor the movement of virtually ever single car on the road - for no other reason than the creation of a 'Big Brother' Tracking System.
The data handling policies associated with this movement toward ALPRs are key.
The police agencies should not be allowed to retain their data for more than a few days. They should not be allowed to "sell" the data. There should not be a massive national "data warehouse" where all of this data is aggregated.
Failing these policies the conditions in the movie "Gattaca" will be upon us.