Well it finally happened to me. My wife and I were on our burley Tandem http://velospace.org/node/3616 going 34 mph and I hit a golf ball sized rock. Instant Flat Tire. I am lucky I was not turning. I was able to maintain full control and bring it to a stop.
This was my fault because I did not air up before the ride. The tires dont stay at 120 for me over night. They drop to about 90-100 and that is just not enough. I wont forget to air up ever again.