This is not so much about privacy so much as being a douche bag. This type of bullshit behavior makes it impossible for real photographers attempting to capture 21st century life the way Garry Winogrand might have impossible. There can never be trust between subjects and photographers. Just try getting model releases if this shit keeps happening.
Let John Kubera know how you feel about his efforts to help photography: http://webcache.googleusercontent.com/search?q=cache:RRba28d...
John is the one on the left with the mustache.