A Harvard professor - Daniel Lieberman - has started running barefoot. His research shows that running barefoot creates less stress on feet because barefoot runners tend to land on their fore-foot.

Runners in shoes usually land heel first. He found that landing on your heels can produce up to 3 times the bodyweight force on your foot; landing on fore-foot produces only 60% of bodyweight. Thus the barefoot runner gets the benefit of using the ankle, tendons and muscles in the lower foot to help absorb the impact.

Makes sense.