In reply to StefanB: Hi, I personally think that we, as modern humans, should not begin to run on our bare feet.
As animals, we are "designed" to run on bare feet as we have feet shaped for an efficient running style, with the arch of the foot acting like a spring board for the next stride.
It is certainly true that running without footwear will make you alter the point of your foot that hits the ground, i.e., the forefoot. This is our natural style. Landing on the heel is inefficient and it tends to happen when wearing soft, comfy running trainers. It is this that we must concentrate on - landing on the forefoot. This can be practiced and achieved whilst running in trainers and it will improve your style.
After we've reached a certain age and having worn shoes all of our lives, trying to run without them is, to me, asking for trouble. We (in modern day living) have almost evolved to wear shoes and we cannot go back to barefoot, hunter gatherer style living at the same time as keeping up with our modern lives. It may be different for today's tribal children who grow up wearing no shoes but for us, we have artificial surfaces, like tarmac etc., to run on with broken glass and dog droppings and who knows what else on the floor.
I think if someone must run barefoot, then do it only on natural surfaces like forest paths and sand.
Cheers.