Entities, i.e. companies, are pretty careful everywhere about publishing photos of people for marketing purposes (which any website is) without permission of some sort. Whether it's in the terms of attending an event or it's a stock photo which presumably has a release form. I doubt individuals in Germany are much less indiscriminate about sharing on Instagram, Twitter, Flickr, and elsewhere than they are most places. And German law has very little teeth if the people doing the sharing aren't German.