Cognitive dissonance is a crazy thing. On one hand I am definitely committed to this whole photography thing. I enjoy walking around with my camera looking for nothing in particular to shoot. There are times when someone is either wearing something that catches my eye or doing something interesting and I'll stop and ask for a photo. Usually I don't do candid "surprise photo" stuff in public. I think that whole in your face street photography style has been done to death. There are times when I'll end up with people in the shot just because they're involved with the larger scene and on rare occasion I have grabbed a compelling shot without asking because that moment was just too good to pass up. When a person just happens to be in the scene they're usually small enough to be unrecognizable as in the example below. Most folks are good sports about it and the people who seem to think every guy with a camera is some sort of Jared Fogle are few and far between.
In the United States the law is pretty clear on this. According to the ACLU you have the right to photograph anything that is in plain view when on public property. This includes people, buildings, and officials. There have been some laws passed in certain locales about not photographing police officers. This also doesn't mean you can get a long lens, stand on the sidewalk and try to shoot in someone's window and on private property the property owner sets the rules. You also can't break other laws when shooting like trespassing, obstructing traffic or vandalism. You also can't take photos of someone on public property where there is a reasonable expectation of privacy, restrooms and changing rooms for example. Even if you can see into it from the outside for whatever reason. On private property the owner or people working for them cannot confiscate your camera. They can just tell you to stop or ask you to leave. Well, they can't take it from you legally but if they're threatening you with a firearm or a good beating I wouldn't argue, you can't get your camera back if you're dead. Just go get the real police if that happens.
Again, these are US laws so please don't use them for justification of public photography anywhere else. Know the laws of the places you intend to visit.
So we have a precedent for public photography being OK. Largely that has been a good thing as it lets the press do their job and allows for free expression, which was the original reasoning behind the legal justification as I understand it. Both of these are important for a world like ours to function correctly and I wholly believe in these principles.
However, most of this was put into place long before the digital age. These days a random snapshot can end up being view by people halfway across the world thanks to things like Flickr, Facebook, 500px, etc. There are also face detection algorithms which a few of these services use to automatically tag someone, along with apps that automatically upload your photos to various cloud providers. This makes for a more interesting set of problems. A photo snapped of a stranger may end up in front of all kinds of eyeballs, unlike in the past, whether deliberate or not. For most people this probably isn't much of a problem. A good part of us first worlders live our lives in public on the internet so a random photo of us walking down a street next to 5-6 Facebook albums of drunk party photos isn't that big of a deal. But there are times that someone may not want their photo plastered all over online. The common response to this is "if you're doing nothing wrong you've got nothing to hide" but it's really not that simple. There are times when people relocate to escape bad situations or other life circumstances. This doesn't mean they're up to something illegal, they could just be trying to remain hidden from an abusive or threatening person or situation. Having their photo online indicating their whereabouts may be less than optimal. These situations, while probably rare, are just a couple of examples of why someone one may not want their photos taken and posted online. Some folks may just want to live online free lives for whatever reason and that's OK too. Several decades ago during the heyday of film photography people didn't really have to worry about things like this. A photo generally didn't travel very far.
I believe that people should have a right to where they want their data stored and how much of that they want public facing. I tend to eschew many cloud services for this reason, only use Facebook/Google/etc for the most inane social interactions, disable location services on my devices, use trust no one encryption when possible and so on. Remember kids, there is no cloud, it's just other people's computers.
So I can see two sides to this argument. In a world where a photo can be seen by thousands of people in a few seconds where does the individual right to privacy end? Should a private citizen be able to ask a photographer not to take a photo or to delete it? Would that potentially be abused by public figures who may be up to no good? What about the media's ability to do its job? What about art? Do the current rules work well enough?
Personally, I'm more or less OK with how things work now. There are some fringe scenarios where everything may not work out but for the most part out in pubic and put on the Internet are close enough to the same thing. That's probably a good way to treat what you do online too. Just because you've put some disclaimer (that I'm laughing at right now) about how private and confidential that your email is doesn't mean there isn't a relay out there with it stored. Use GPG fool. Same goes for Facebook messenger, etc. But I digress.
Moreover, the press and people documenting public officials are protected somewhat by these rules. This is probably one of the most important things to keep in mind. Sure, you might not like that random guy taking photos on the street but there are others who depend on these rights and ultimately we all do to some extent. However, it is good to sit and think about these things every once in a while. Things change every once in a while these days.