It is unreasonable to expect to not be observed in a public place, but it is reasonable to expect to not be recorded artificially without your knowledge. This goes for all locations, including public ones.
I am aware of tourist photos and photos by friends. It is reasonable to expect that I'll be in occasional photographs where I am not the subject. I know that. It is reasonable to expect that I won't be the subject of photos without my knowledge or included in detailed photographic records just because I went to a public place. Detailed imagery of your whereabouts and activities should never be expected and should only be legal with a warrant.