The force on the QR is exactly the same with disc-brakes as it is with rim-brakes; they both push the hub & axle backwards while the fork & frame tries to continue forward. This real problem is people not tightening their quick-releases correctly. An age-old problem with bikes and people not knowing how to use their equipment properly.

Heck, I've worked in a bike-shop for 10-years and I made an idiotic mistake this last weekend. I swapped in a new wheel and it turned out the rim was 2mm smaller in diameter than the Mavic rim I had on there before (Mavics tend to be oversized). So... I didn't check my brake-pads and they were now riding 1mm too high... Guess what? In less than 30-minutes later, I had a flat-tyre... Am I gonna blame the shop that sold me the new rim? Or Mavic for making their rims slightly too large? Or sue Shimano for making brakes that don't automatically adjust themselves to center the pads on the rims?