Very good post, Andy. I think this whole thing about "choking" is very misunderstood.
There are runners who can't deliver in pressure situations, but most of the time when outstanding runners fail there is an explanation (which is different than an excuse): They were injured, sick, or improperly trained.
I knew a runner at Stanford who specialized in finishing second. He was a talented runner. He'd been second at the California H.S. State Meet and had a full athletic scholarship, but throughout his time in college he specialized in finishing second (or lower), whether it meant running a 1:49 half-mile or a 1:54. THAT's a species of choking. Otherwise -- I haven't really known that many athletes who honest-to-god choked when it counted, simply because they lacked courage or resolve.