There should be a way to set the priority order of devices used for audio and video out and in
Computers these days don't have a fixed set of hardware devices, it can completely change in a moments notice.
For example, a microsoft surface device could be plugged into a "docking" station, and using the video card in the keyboard unit, a camera connected to the keyboard unit, a professional usb microphone connected to the keyboard unit, two large 32" screens are used for display. With a keypress, every single one of those units goes away. And the other way around, when the keyboard is plugged in, these devices show up and become available.
Whenever something like this occur, skype need to know which of the new devices it should use for what.
Sky CAN NOT, AND SHOULD NOT pick the first device it find and just use it!