Well I suppose it depends how clumsy you are!
Seriously, all I can say is that the shear bolts have saved me twice; once when the bike was knocked over by boy-racers in a car-park, and once when I caught the mirror on the gate post (
).
I wouldn't expect those cantilevered brackets to stand up to a full-scale 'drop', but I still think the shear bolts are a good design feature.