That’s not really much of an argument: “it already happens, so what”? People still have a reasonable expectation of privacy, even in a public setting, say you’re having an argument with your wife and I’m recording it. You certainly won’t like it if you see what I’m doing, and you have no idea if I’ll upload to a site that implies “the men in these videos have anger issues and probably beat their wives.” This is hyperbole, yes, but it underscores the issue: when you’re on the receiving end of it, will you just keep arguing with your wife or demand I stop? Might be an interesting case.
No, it’s not a non-issue. I can take a picture of you on a public street in front of a McDonald’s, but I can’t use that to promote McDonald’s and imply, by your visible face, that you’re also “lovin’ it.”
Something always has to happen to someone before they stop being blasé. Think of it this way, when you’re in the locker room at the gym, someone walks in wearing Glass, you’re probably going to pause a bit, even though you are aware of surreptitious cameras in gym bags having done the same thing. A locker room is not a public street, but you do have an expectation of privacy.