The proprietary technologies employed by the major shoe manufacturers (Air, Shox, Gel, etc.) seem to be the limiting factors in terms of shoe breakdown. I can't count how many times I've had to stop running in a shoe because the "gimmick" failed (i.e., popped Zoom Air unit), despite the fact that the outsole and upper showed little signs of wear. The purpose of a shoe is to reduce friction on the foot when running on unnatural surfaces like concrete, not to employ technologies that provide over-cushioning during their early lives only to fail after extensive use.
It seems like Nike, Adidas, and the other footwear companies don’t understand this problem. If any of you recall the Talaria, it was an awesome shoe until the sensitive air membrane on the sole ruptured. Nike somewhat solved the problem with the early Elite, but then proceeded to completely change the shoe after the next design iteration. New Balance had a great thing going with the RC-150, but it was discontinued. The design of the Puma H-Street was on the right track, but it was marketed as a fashion shoe. I don’t know about you, but I’m still waiting for a serious, resilient, lightweight, minimalist flat/ trainer.