To say that Flock is either bad or good is highly oversimplified. It's much more complicated.
To begin with, anyone who thinks that they have privacy of the location of their face, body or car when out in public is "in a state of sin". The words "public" and "private" along should give that away. If I'm out in public, and looking around, then simply observing other things visible in public can not possible rise to a search, much less to a 4A unreasonable search. Nobody can claim that it is illegal to walk down a street, and seeing that Alice is walking around holding hands with Bob, or that Christine is driving David's car, or that Eve has gained 20 pounds and might be expecting a baby. And it doesn't matter whether the person doing the seeing is an individual, a government employee, a company or a government agency, or a camera operated by those people.
We can discuss the details of what "public" means, but they don't matter much for this topic; a normal street is definitely public. Whether parking lots and shooting range driveways are public or not is complicated, and a different discussion.
But what is certainly true is that technology is changing the economics of doing this. In the old days, only rich people, big corporations, and big government agencies could perform this "seeing" function on a large scale. If I am rich, and I have an adversary, I can hire a PI (private investigator) who will wander around in public and look for my enemies Zachary and Yvonne, and send 4 or 6 people per shift to just hang around near Z and Y's house, notice what car they're driving, watch where the car parks at the shopping center, wander around "not quite aimlessly", see what stores they go to, see what bank they are depositing checks at, see what color their credit card is when they pay for groceries, and so on. This is actually commonly done for legal disputes, for example if I am Zachary's soon-to-be-ex-wife looking for what he's doing with Yvonne, or perhaps I'm a creditor of Z and Y and need to know where they keep their money, and how to serve them a "write of execution". Anyone who claims that privacy exists because people can't be traced does not know about the real world of legal processes.
All Flock does is scale this up, democratize it (it becomes much easier for anyone to do), and give people tools to access this data. Now, the data collected such can be used for good and for evil. For example, the data could be collected, organized, and sold to law enforcement agencies under the restriction that it is only to be used for targeted searches, and only with court-approved warrants. Warrants that are issued by judges who are knowledgeable about the technology. For example: Michael has just murdered Nancy and got caught in flagranti, and the cops need to know where Michael was the day before, what car he was driving, and whether he met with any of Nancy's other friends and enemies. For that kind of thing Flock is great. Or Michael was just seen murdering Nancy, and we suspect that he's going to kill Oscar and Paula next, but he took off in a white Corolla with license plate 1ABC234, and we need to URGENTLY know where he's going so we can protect Oscar and Paula and catch Michael.
This is the reason why police agencies LOVE Flock (and other similar technologies and competitors): It allows them do to a better job, catch more criminals, do so with less budgets, fewer mistakes, and less intrusive work. What's not to love here?
Great. Now the counter-example: Bad cop Harry is suspecting that his girlfriend Irene is cheating on him. So he logs into Flock, types in a fake or different warrant number, looks for all movement of Irene's car, and find that she often goes to Jerry's apartment at lunch time, and comes back out looking flushed with her clothes in disarray. Clearly, Harry does not have a real warrant, and the misuse of the Flock data is both illegal and immoral. I think everyone agrees that this is bad. We can argue whether Irene and Jerry are doing the right thing or not, and whether Harry should know about their antics, but it's obvious that misusing his department's Flock access that is supposed to require a warrant is bad.
Now, many people are willing to to throw the baby out with the bathwater: Flock must be made illegal because of Harry. That's like saying that all guns must be made illegal because someone just committed a murder with a gun. Sorry, wrong reaction. Harry needs a spanking, because that's where part of the problem lies. Perhaps Harry's department needs to be kicked in the nuts to implement some more sensible access control to Flock data, or some auditing of what it is used for, and perhaps write a policy manual.
Then there is another set of people who think all government is evil: anything that gives government more power must be bad. They are sort of anti-government "anarchist" luddites. There is a significant overlap with another group, namely criminals, who enjoy not being seen. Today, both groups think that they have a measure of anonymity when out in public, and they don't like Flock, nor do they like cops and law enforcement agencies in general. To those people I say: First, you are deluded, and are much more visible than you think, simply because a well-organized investigator (whether private or public) can find out a lot of your habits, whereabouts and actions by just asking the right questions and doing legal things. Second, society changes as a reaction to technology; just because something worked a certain way in the past doesn't mean that it needs to work the same way in the future.
The argument "Harry did something bad, therefore we need to punish Flock" can be re-phrased by saying "some LE agencies have been bad, therefore all LE agencies are evil and we must never do anything that makes their work easier or better". It is certainly true that some LE agencies and some of their members have been bad. Gun people very often get really worked up over that, and I just need to give the example of Iggy to start some people (righteously) foaming at their mouth. But the fix for some LE agencies being bad is not to throw all LE and their tools out. Even though anarchist radicals and career criminals would like that.
More opinions on Palantir and other such things later, when I have more time.