Interesting idea. If the wire leads on your internal USB cable is made long enough it looks like it would not be difficult to just remove the cover and lift the attached arduino to the side of the netbook. That way you could access the pins for actual hardware testing. Don't know if the Arduino mega footprint would fit in there, but the Seeeduino mega has the same footprint as the standard arduino plus uses the smaller usb connector.
Too bad the only lap top I own only runs windows 98, I don't think it can run the arduino IDE.
Lefty