Most of the cameras are attached to either Apple or Android devices. The companies that control these ecosystems could use them for mass surveillance. The government could 'politely' ask these companies to do that for them. Or they could just directly order the phones.
Sort of except for the fatal flaw that you are talking about battery powered devices that mostly live in peoples' pockets. The reason Flock cameras and Ring doorbells both serve well for mass video surveillance is consistent predictable location and power.
Maybe, yes. On the other hand, there's lots and lots of people running around with these things, so you get pretty good statistical coverage, especially in cities.
Unless we are trying to do the "conspiracy theory" route: there is not "thinking" here. You can at least sniff traffic or whatever and tell if your phone is ringing back to google even when you tell it not to.
And the discussion above is about a different kind of surveillance. Notifying Google (or state) that I'm sitting in front of my PC is one thing. Sending photos of videos of me jerking off is different.
