my first thought seeing this topic was exactly what Doug said.....I have always kept a camera in a handlebar bag, easy to get to and if the bike falls over, it doesnt impact the ground.
Certainly a downside to a larger camera that wont fit in a hbag, and exactly why Ive always used point and shoots , smaller cameras than real bodies and larger lenses, both in the film era and digital (plus I dont want the weight and worry about an expensive doohickey).