Haha, not really. The idea of window air conditioner falling through a window over a car is just a myth in the movies or advertisements. You will rarely ever hear that a window air conditioner fell from the window and hurt someone. Granted it does happen, but it it would only occur if someone messed up. If you have done your job correctly (or your hvac contractor), a secured window air conditioner will stick to your window like a bug to a windshield, it wont budge. So no, window air conditioners are not dangerous.