>Public streets are fair game for anyone with a camera, and that includes the police. It's best if that doesn't change.

While this logic, the "no expectation of privacy" principle, has long been the standard, and is certainly the logic law enforcement and businesses like Google push hard, I think we really do need to have a public discussion and consideration of how technology enabled Emergent Effects, with emphasis, creates new phenomena that are simply completely beyond the realm of human-oriented common sense that was operated under before. Yes, any single human has always in principle been able to happen to see an individual instance of something in view of public property, or follow somebody around, at any point throughout human history. With the advent of the camera, they could even possibly make a clearer, permanent record of that, but that didn't really change much either. Even simple basic video tape was a true shift.

But the ever increasing volume of storage and processing available at ever shrinking cost, combined with similar cost/quality improvements in sensors, objectively changes the situation. Even if it's 100% purely on public property where there is "no expectation of privacy" and involves nothing but video, a ubiquitous surveillance system plugged in to sufficient persistent storage and data processing creates capabilities that are on a different level. It equates to effective location tracking of any individual for a start, but additionally allows inferences to be drawn about everyone they meet with. It becomes possible to start back tracking people's relationship network graphs, and discerning all sorts of higher level private information. The most simple classic example would be knowing John Doe visited a private residence late at night with Jane Doe who is not his wife in a repeated pattern, and boom, blackmail material, but it could easily be used to make high-accuracy judgements on everything from health issues to private interests to overall group memberships.

This is a huge amount of potential power, and it's objectively something very very different from having a single warrant for an individual and having some investigators try to follow them around. Resource usage matters: in the end, all security is fundamentally an economic equation. If an adversary, or even an agency that nominally is supposed to be on "our side" can suddenly do a technique 100000x cheaper and more effectively then it cannot necessarily be judged by old standards. Emergent effects or properties that do not exist in a lesser collection of individual parts are a huge deal in all parts of our world, and they're becoming a big deal for information now too.

We really should not just allow "well, the police/military intel/investigators/big data corp are only doing what any individual could except a billion times more" to go unchallenged, because that "except a billion times more" is a huge deal. No, an individual human could never do that sort of thing themselves, or even with a huge group. Even the biggest, best funded police states of a half century ago, using far more intrusive techniques, couldn't manage the kind of efficient ubiquitous population categorization, information gathering and tracking now becoming possible "merely" through what's available from the sight of public roads. Don't dismiss what a change omniscience makes. I really hope the courts start to recognize that at some point what government is asking for is not a simple extension of what they've always had, it's something entirely new.