A potential harm would be if the images that are being captured are of young children or certain other types of vulnerable people. There's the potential harm of humiliation if the images are continually capturing, in certain cities, some people who are intoxicated for whatever reason. The images would reflect badly on them or humiliate them and cause them various types of personal harm.
That's the type of potential you would have if you allow Google to use a journalistic exemption; it would open the door to other types of surveillance.