Personally, I've never broken a hub axle, but I've certainly bent a few.

Hey, it happens, and now I'm replacing a lot of them for customers. Usually it seems to happen because a bearing lock nut gets loose, the balls run out of their race and start running on the axle on one side, and the weakened axle snaps after a seemingly insignificant hit. The quick release skewer holds the hub together until the grinding, squeaking, wheel wobbling, and poor braking drive the cyclist to the shop to "fix the back tire."

The best solution is prevention. Examine your wheels regularly and get them adjusted or overhauled at the first sign of trouble. And there's no reason to tolerate getting yelled at by a shop mechanic.