It's not about scale, it's about oversight. A warrant puts a lock on the data until the request is approved. Leaving it wide open is the reason we have constant news stories about police being arrested for stalking people. Nobody wants to limit the police's ability to investigate crimes, but we do want them to use their power to investigate crimes, not to stalk their baby mama, crush, rival, etc. I fully understand and accept your point that there is no real difference between a cop watching and the cop setting (or hiring) a camera to watch, and I even believe that the more data available the more humanity benefits, and that a total absence of privacy as we know it is inevitable, I think we are not there yet culturally, so strictly requiring warrants for police to access these systems is desirable.