Once the police started to record every interaction with the public, along with their existing habit of placing traffic cameras left and right, they acquired enough data to track people.
Trying to restrict the analysis of existing data is never going to work. The police can always point to some death that wouldn't have happened, if they had ran Flock's software on their surveillance footage.
And even if by some miracle you manage to forbid plate recognition, cross referencing, etc, every ambitious (or lazy) detective would start doing it on the down low with OSS software.
I was sold during the recruiting process on high ethics and morals and an idealistic vision.
The reality was a surveillance state, questionable policies on data sharing between agencies and private installations (HOA, etc.), and a CEO with a very literal belief that Flock should "eliminate all crime" - not "visionary" but far more literal. It was way too Minority Report for my liking.
They have a public "disclosure" site that supposedly shows the agencies using Flock that is absolutely inaccurate (there are three agencies in my County alone using it that are not listed there).
Any conversations about ethics and the other "should we even do this?" questions got consistently shorter and superficial during my time there.