However, there is more to it than that. There is a biomechanical basis for barefoot training. Force plate (measuring how hard the foot hits the ground) analysis shows people will strike the ground harder while walking with shoes than barefoot. This makes sense. You are not going to slam your heel into a hard surface. You can feel the discomfort immediately if you did. This is exactly why barefoot training is easier on the foot (and knees, hips, and spine). You can more easily sense pressure on your foot while barefoot (or wearing a very thin sole like the Five Fingers).
When walking or running barefoot, you will land on the forefoot or mid foot and use you calf as a shock absorber as it gently lowers your heel down. This technique helps spread the force over the entire foot, not concentrating the pressure on the heel. See drawing below.
When wearing shoes, you are more inclined to strike the ground with your heel first. The shoes do cushion the force somewhat, but more so, they dampen the nerve's in the foot ability to sense pressure on the foot. See drawing below.
Additionally, the lower heel while barefoot (or in Five Fingers) adds to foot and ankle stability. How many people sprain their ankle while barefoot? Single leg stance is also enhanced as the toes are able to spread and grip the ground.
Makes you wonder why you would spend $160 on the latest high-tech running shoes?