I'd like to add that mechanical shock absorbers are an absolute must if the camera is mounted on the bike. I've destroyed a camera before. You wouldn't believe the amount of shock the bike has to handle even on normal paved roads.

Also, the in-camera electronic image stabilizer is not needed when using mechanical shock absobers. In fact, EIS tends to blur the video (on my Panasonic PV-GS200, which does not have a reputable EIS system). A mechanical image stabilizer however should be useful. But I doubt any consumer grade cameras have that...