All of those professions are licensed and bonded so they are supposed to know where that legal cliff occurs and avoid going over it. Your average layman most likely doesn't know the boundary between completely public and public privacy.
So, let's say I picked a random person on the street, followed them around all day in public, do not intrude on their space or enter premises where I'm not allowed.
I'm not licensed nor bonded in any way of any profession.
I wish there were something that you could be charged with. If someone is charged with something that's society's verdict that something pushes the boundaries of what's acceptable and a judge needs to look at it. Seriously, following around a random human all day, what does that do for him except push boundaries?
Also: collecting data on a human by a human does not scale. Large-scale automated data collection on the other hand takes on a wholly different character. Let's say someone became your political adversary fifteen years from now and you don't know it today because he is in college. You needed to dig up dirt on him, and you find out that while in college he was a prolific consumer of "My Little Pony" porn. Automation makes such a scenario possible. Without it you would have to send staffers through archives, and that's only worth it for the biggest targets.
I'm not disagreeing with you, I'm just trying to point that, in most cases, it is legal to follow someone around regardless of whether you have a form of license provided by the government.
