I read somewhere, can't remember exactly where, that if you're in public, you give up your "right" to privacy. You are in the public view, and pictures can be taken. If you used a long zoom, and took a shot through someone's window, you are invading their privacy. But, other than that (and, of course, such examples of shooting up a skirt), then anything that you can see, can be photographed. I thought it became an issue when you published pictures, for profit.