An article , linked by Slashdot.org addresses the need (or NOT) for running shoes. I am interested, as I was into the habit of using no shoes at all, in Chuuk. I scorched my feet pretty well on a midafternoon, walking up a highway in Kona Hawaii from the City of Refuge to Painted Church. After that, it was quite easy for me to walk barefoot anywhere. Gravel. Reef platforms (very difficult to do otherwise). I gradually built up thick soles on my feet.
In Chuuk, on the island of Tol, I walked daily to and from work, between Wonip Village and Foson, where I worked, almost always without shoes. Since leaving Chuuk some 14 years ago, I have probably lost a good amount of my callouses, but I can still walk in many situations without shoes. I was able to walk the rocky pathway over a mountain saddle after dark, on a moonless night, by feel. I wonder how I did that, even now. With shoes, I think it would be impossible.
This article mentions that the Stanford running team decided to train barefoot. Apparently the use of the most technologically advanced shoes caused most injuries.
In my case, I earlier had heel spurs, so I now use air-nikes. "Money won't change you, but time will take you out."