Or other private citizens. What’s stopping someone from creating a mesh of ring cameras and using photos scraped from social profiles to let individuals track one anothers‘ whereabouts in real time?

Technically? Nothing. Legally, this would be huge privacy incursion. In the EU, we have, among other things, (usually constitutional) right to privacy, anti-harassment and anti-stalking laws etc.

Also logistically, it is nearly impossible. The idea falls apart when attempting comprehensive surveillance. There is simply too much noise and too much uncertainty from the low quality, at distance, uneven illumination video. I write FR software, and large installations typically fall apart because the humans are simply too lazy, they delegate too much that should not be delegated, they are lax and frankly incompetent. Outside of developing tech orgs, FR is too complicated for under-educated persons like the police. At minimum, you need to understand probabilities better than a typical consumer.

How does cross-camera object tracking fare? Don't need to recognize someone if you can follow them until you see their face or their car or destination clearly.

I wouldn't have a huge problem with it in particular not if it includes the authorities themselves.

I used to see privacy as empowering but I've changed my opinion more and more to seeing transparency as more important, across multiple dimensions, not just policing.

Whether it's tax avoidance and financial havens, human trafficking scandals, sexual abuse victims being empowered by social media to communicate and hold people accountable, watching the police (very relevant), it seems more and more to me that privacy is mostly a tool for the individually powerful whereas transparency is a tool for collective action and impartiality.

I don't see how it matters.

For all I know I'm being tracked in that way by satellite already. It's only when things become operative, of someone harasses you or something ... but then they'd be easily traced and prosecuted.

In short, I'm not sure I care.