Could be, sure. And anyone could wear a hidden camera and secretly take your picture, or a wire and secretly record you.
If any of those undercover archivers re-publishes your content, send a DMCA notice and sue them. Where copyright infringement is a crime, report them.
There's a cultural component to this, I believe. Americans seem to feel that pictures, recordings etc taken in public are fair game, continental Europe has a different stance. Even in public, you can't take pictures of ordinary people and publish them (unless they're part of an extraordinary event).
I don't know which European country you have in mind specifically, arguably some are more strict on this than others(Germany, Austria) but most places you can take and publish pictures taken in public places without asking for permission. It's only an issue if someone is specifically a subject of your picture - so a wide shot of street is absolutely fine, but a photo zoomed in on someone's face is not, even if they were in a public space.
Some also allow news content in general, even if the picture itself isn't noteworthy (i.e. illustrating a shopping mall vs somebody standing next to a politician being attacked with a cake), but I don't know about the intricacies.
I'm European, but I fail to see how anybody could have any expectation of privacy when in a public place. You either outlaw camera's completely or you have to accept that you might end up in the background of somebodies photograph. I don't think outlawing camera's is realistic.
You don't need to outlaw cameras any more than you need to outlaw knives to keep people from stabbing others. But as mentioned, there's a fundamental difference in the idea of privacy, I suppose. It can be understood as "something that happens in a non-public place" or it can be understood as a larger idea that you have a certain right to not be surveilled, recorded and stalked.
I guess that I find the idea that you should expect privacy when in a public space kind of strange (its right there in the word: public), but that doesn't mean that I think its ok for someone to follow you around recording you (but not because of the actual act of being recorded, but rather because of the targeted nature).
Similarly, I think passive recording (ie non-targeted surveillance) of public spaces should be allowed in and of itself, but that its the use that dictates whether its abusive or not (ie if its done so that people can be identified, then that seems similar to me to following someone around, but if its done for the backdrop of a movie or art project, or its done to study foot traffic on a street.. basically there are many reasons which aren't abusive).