Those of you on this thread that are minimizing the odds of and severity of cougar vs human attacks simply have not spent enough time around them and you are begging to be DEAD WRONG about this!
I've been around and encountered pretty much every predator that you can encounter out west. Cougars are the only animal that I've seen that will routinely hunt humans.
Cougar attacks are a normal, common, thing in Colorado. General rule of thumb is if you are their size or smaller you are considered prey. They are ambush predators that for all practical purposes are silent. While they are stalking you they know you can't hear them and have no fear of you! I had to explain to a good friend who came from Ohio and bought a ranch that no his dogs wouldn't scare them away, he needed to carry to defend himself and the dogs.
Gaily bedight, A gallant knight In sunshine and in shadow, Had journeyed long, Singing a song, In search of El Dorado