There's the argument that this is just scaling what used to be done by human police on the beat watching for suspicious behavior or known suspects. That doesn't require a warrant in public spaces. Now we can do this at scale with technology. Does that change the equation? I think it does. I struggle to find a legal argument against it, but I just don't think that's the kind of society most Americans want to live it. And it opens the door for abuse at a massive scale.