What???

Derailleurs are not weight bearing, so I'm not sure what one's weight has to do with their usability or durability. Cycommute addressed this - the derailleur likely got pulled into the spokes due to either a bent hanger, operator error (poor shifting) or a poorly adjusted derailleur. I suppose it could be that the wheel deflected due to the weight it was bearing and that resulted in the derailleur hitting the spokes but, again, that is not related to the derailleur bearing any weight, because it doesn't.