@iJon: Don't tell me you read all that and the links in 9 minutes.
Yes, my plan was to buy a pair of Vibram FiveFingers for running. I live in Australia, and they're very hard to find here, so I gave up on the idea. However, I found them in a shop in Sydney, and I finally had a chance to try them on. This renewed my interest, and I did a LOT of reading.
I read a number of articles on the benefits of running barefoot. All of it sounded good, but I had a couple of questions I wanted answers to. The question I had that's most relevant to the thread I linked to was:
While running barefoot is, obviously, a very natural thing to do, is this also true when you run mostly on concrete? After all, the forces are completely different than they would be if you were always running on grass and dirt/earth.
Well, it turns out that the answer my question was, "Absolutely not." I asked myself that question because running barefoot on concrete didn't sound any more natural to me than running in proper shoes in a grassy park.
Anyway, I just thought I'd share.
It sounds to me like barefoot running and walking is absolutely OK, as long as you're not using them primarily for distance running. I agree that barefoot walking or running is natural, but humans were never designed for the rigours of running on asphalt roads and concrete sidewalks. They may (or may not) help strengthen your feet, and may (or may not) help your running form, but there's no strong evidence that clearly indicates that running barefoot prevents injuries better than a good pair of running shoes.