If you find yourself sympathetic to Flock, you should ask yourself: do we have a right to any kind of privacy in a public space or is public space by definition a denial of any sort of privacy? This is the inherent premise in this technology that's problematic.
In Japan, for instance, there are very strict laws about broadcasting people's faces in public because there is a cultural assumption that one deserves anonymity as a form of privacy, regardless of the public visibility of their person.
I think I'd prefer to live in a place where I have some sort of recourse over when and how I'm recorded. Something more than "avoid that public intersection if you don't like it."