The only people who still worry about Kinect always on are conspiracy theorists or completely missed MS explaining all the customizing and disabling options... it does not pose a threat to anyone's privacy any more than a webcam on a laptop does.
They require it connected because it is an input type that is fully integrated with the console. Do you complain about not being able to disable a controller as an input device? No, because that would be silly :)
if you're paying any attention to the NSA scandel you'd know that the US governement has given themselves legal right to access communication regardless of privacy policies and that MS was one of the first partners of the NSA. so "no more than a webcam" is sort of a loaded statement..
sorry, but i do NOT trust the us government right now with respect to privacy.