Even in Germany this is legal. The right to photograph someone is usually delineated by the principle of "reasonable expectation of privacy". Note that this is a legal term that has been defined both through legislation and via decades of case law in many countries - so personal definitions of it don't apply here.
Common places where courts have upheld the reasonable expectation of privacy include restrooms (including public ones), a home, a hotel room, etc. A conference talk is not one of these places. Which is to say, people are free to photograph at will.
Note that should the property be private, the owners (or agents thereof) are entitled to disallow photography. Note also, importantly, that the right to disallow photography does not include the right to confiscate any photographs already taken. The most the property owner can do is remove the individual from their premises or have them arrested for trespassing.
Note also that while photographing someone in a public place is not a violation of any criminal law in most Western countries, it does not shield you from civil liabilities - you can still be pursued for damages, libel, or defamation (which seem like it may be relevant in this situation).
There are some countries and territories with substantially stricter laws regarding the likeness of people. Japan and Quebec for example are places where the right to photograph someone in public is not protected by default.
As you correctly stated, taking photographs is very unregulated (and wasn’t regulated at all until a few years ago) in Germany. It’s only illegal to take photos in the places you listed. (Actually it’s not so much about specific places. The photos have to invade a private area of life, though that usually means places like the home, hotel rooms or restrooms are off limits.) This barrier is actually relatively high, not everything is immediately an invasion of a private area of life, even if it might seem so. A normal shot of you hanging out in a conference room with hundreds other people? Not an invasion of a private area of life.
This also means that privately owned but public spaces are not included there, like, say, conference halls or train stations or shopping malls and similar such places. As you also correctly stated, the owner can disallow photographs, though by default (i.e. if the owner doesn’t have any rules) taking photographs is perfectly ok.
The issue is publishing photographs. There the barriers are much, much higher in Germany. If there are people in it, the default is that you are not allowed to publish them unless every person in the photograph agrees. Now, as always with the law, there are (of course) exceptions (e.g. if people are only incidental to the photograph and not the main subject, say if you take a photo of a building and there happen to be a few people in front of it), though none of them apply in this case. Publishing this photo wouldn’t be legal in Germany (taking it would), though it is important to note that in Germany those depicted in the photo would have to come forward and press charges. Otherwise the police is not allowed to investigate or charge people. (You could say that the default assumption of the law is that everyone in published photographs agreed to it and if you don’t it’s on you to come forward.)
However, that is not the case in the US where both taking and publishing this photo is perfectly legal. So I do not really see the relevance of this discussion.
It's a shame, IMO - Europe is the birthplace of photography, and of street photography in particular, and we are still reaping the benefits of the historical record provided by decades of laissez-faire attitudes re: photographing strangers.
You don’t need permission to publish photos of historical significance. That’s pretty much why newspaper photographers can exist in Germany. All those kinds of photos – if they do not invade some private area of life of the depicted persons – are totally fine.
As I already mentioned, the same is true for photos in which the people are not the main subject – though if some person is easily identifiable you likely do need their permission, even if they are not the center of the attention. This exception is mostly so that someone ten pixels in size or so cannot rain into the photographer’s parade.
Or – and this can apply to street photography – if it serves a higher interest of the arts. I think the general recommendation for street photographers is to make eye contact with who they photograph and check that way whether it’s ok. Also, walking up and talking to who you photographed isn’t super hard. As I already said, photographing without publishing is nearly always ok, so you can shoot first and get permission later. Also, since those depicted actually have to press charges it’s not like the police will bust your exhibition and confiscate your photos. Someone who is on some published photo has to complain. And even then there still is legal wriggle room. The right to privacy is one of the rights defined in the German constitution – but so is the freedom of the arts. If those two collide judges have to weigh them against each other and decide which wins. I guess shots of someone picking their nose in public might might make privacy win, shots of someone drinking coffee in a cafe might make freedom of the arts win. (Also, it’s not like this is a felony. It’s a private law issue.)
Photos of assemblies or demonstrations or similar such events are also ok. Huh, now I’m questioning my statement that the published photo is not covered by one of the exceptions. My interpretation of this was always that this covers all kinds of political events. Being able to publish photos of political events or demonstrations is important for a democracy, that’s the light in which I always saw that exception. However, the actual text of the law is very generic and probably makes reference to all kinds of events, not just political ones. I wonder how the courts interpreted this in the past.
So I guess I can’t say after all whether publishing the photo is ok – not the least of which because the paragraph ends with a sentence that screws up all clearly delineated lines: All those exceptions are null and void if those depicted have a justifiable interest in preventing that. So an exception of an exception.
Now I’m frustrated. And actually want to study law.
That's insufficient for the sort of photography I mean. There is a tremendous amount of historical value provided in even shots of the mundane. Look up the works of Henri Cartier-Bresson, Garry Winogrand, Treng Parke, among many others - these are photographers who captured regular people, in regular situations, in daily life, and in doing so provide a valuable historical record decades later.
The historical record of a people is, IMO, not embodied in photographs of famous politicians and actors, but rather in regular people - and to disallow their photographing by default inhibits this. The concern isn't just historical, it's also artistic - if we disallowed photography of people without explicit model releases almost all of the photography in art museums today would not exist.
> "Or – and this can apply to street photography – if it serves a higher interest of the arts."
That's an incredibly vague - and conservative - angle on it. Street photography has traditionally pushed the boundaries of what society finds acceptable, and for the most part it is always vindicated over time. Most of the challenging, worthwhile street photography would not hit the "higher interest of the arts" bar at the time they are taken.
Your standard basically means that whatever is being done has been accepted by mainstream society already as a valuable art form. Now tell me, how much of new art is already accepted by society at large at the time of creation?
Take a look at, for example, the work of Bruce Gilden, whose working method is still controversial today, but I for one am glad he has the freedom to do it.
> "I think the general recommendation for street photographers is to make eye contact with who they photograph and check that way whether it’s ok. Also, walking up and talking to who you photographed isn’t super hard."
I do street photography almost every day. I know this - it's easy to get permission, it's hard to shove a piece of paper in someone's face and have them sign their legal rights away. The bar isn't "subjects should be consenting", it's "subjects should have signed a legally binding agreement". That is the part that is unreasonable.
> "As I already said, photographing without publishing is nearly always ok, so you can shoot first and get permission later."
You want to track a stranger on a street down later, put a legal agreement in front of them, and get them to sign it?
> "The right to privacy is one of the rights defined in the German constitution – but so is the freedom of the arts."
All around the world, almost universally, the protect of the "arts" extends only to what has already been deemed acceptable. Street photography still isn't recognized consistently as an art form, much less a protected one. Like I said before, to define acceptability as "worthwhile arts" merely protects what doesn't need protecting: art forms that mainstream society already finds palatable and desirable.
However, normally this has to be made explicit (through signs, or the like) - it's assumed it is allowed unless otherwise stated.
I wonder if going forward conferences will consider banning photography in future, for better or for worse.
The photograph doesn't seem to really be the issue, just an obvious thing that Adria did "wrong" for people to seize upon.
It seems like the exact same situation could occur if she had simply reported them through their names rather than through photography.
(There's other stuff that comes into play when you try to profit off such photographs, so the situation can get more complicated than that.)