An interesting perspective on Automatic License Plate Readers (ALPRs)… bring the costs down, and you reduce need for unnecessary data retention.
“Right now the big government agencies, they spend so much on these cameras that they want to catch the bad guys, but they want to get a ton of value out of them,” he said. … “they think that we want to save this data. That’s kind of dangerous. Whereas if the price of these cameras was 10 times cheaper, that need [for long-term retention] isn’t there. I think you don’t even need retention if you have adequate coverage.”
Source: New software watches for license plates, turning you into Little Brother | Ars Technica