I've seen a lot of people hit hurdles. It's tough every time. Probably the worst was Steve Slattery at the Big 12 Championships in 2002. He did a windmill flip over a steeple hurdle after hitting his shin. Looked like it hurt, but he got up and kept running.
My heart goes out to Lolo Jones. She was ahead and on her way to gold when she hit a hurdle. We all hit hurdles, usually of a different type. But I always hope that when we do, we come out stronger, tougher, just as she has shown she will. A true champion. (Video here)