Actually, my point was a little different. I'm saying that, for certain people at least, if you take off your shoes and allow your soles to give your CNS proper feedback, stride length will optimize by itself. It seems to me the 180 rule is most helpful for shod runners, who lack good proprioception from their feet, or, as others have pointed out, for barefoot runners who haven't run or played sports much before, although I remain skeptical about this second point.
I don't know if posture per se affects cadence, it's an interesting question. Good posture will take care of a lot of form issues though, which will help prevent injury, which is the second argument for an artificially high cadence. But good posture is important in every activity, including sitting, so it's not really something you want to ignore, no matter what your stance on the whole cadence issue is. And I don't think good posture is artificial. It's something we unlearn as we grow up spending so much of our time sitting and slouching, just as we unlearn good running form when we become inactive or put on inappropriate footwear. But as many folks have pointed out, young children tend to run with short strides and forefoot landing naturally, and they also stand up straight!
But, as Chris said, genug!
