It's been building with every school shooting, public gun violence, and high tension political gathering. The conversation takes place at the local level, often at the specific school itself, the specific campus, stadium and shopping district. You see, many of these places are private, so they can do what ever they want to a large degree; and many of the public spaces are patrolled by private security companies, who use the most cost effective method to cover large areas. The police are the end of the line as far as deploying facial recognition.