Gareth Libre wrote I have been working on bikes for a few decades now. Starting with the British 3 speeds that everyone had in the early 60's. I took apart many of my friends bikes and my own and my brother's. I never saw, or think I never saw a bent wheel axle nor a bent crank axle.
Following on to his comments and weight being one of the reasons I believe the main cause in my experience is the road surfaces which are left neglected by the higway authorities . Carriageway repairs are are a low priority in the UK and many defects are left in a state of repair for long period of time. I personally have never experienced a bent axle only complete breakage on a few occasions. They have always been the hollow QR spindle especially the type with a raised shoulder for the cone to tighten up against. Ofcourse the quality of any hub must be a factor with lower budget being more apt to wear and tear than the more expensive sets. Pot holes in the road and jumping the kerb stones do no good to any axle but the off road material appears to manufactured to guard against any risk of damaging either hub or crank axle. I pass on the bent bottom bracket axle as I've never heard of this happening in my experience!
Doug Smith
North Dorset
UK