This is the magic question. And the problem with magic questions, of course, is that there is no magic answer.
For those with some type of logic function in the brain, this is a big issue. After all, shouldn't it be reasonable that, if we were all to take our shoes off and run, that our form would be relatively the same? But how is that even reasonable? What about those of us with functional or true leg length discrepancies? What about those of us who have shorter Achilles' tendons? What about those of us with chronically tight calves, putting us susceptible to plantar fascii injury?
But, barefoot advocates say, what of the Harvard study that says running barefoot reduces impact force? Running in shoes, the theory goes, allows us to put more impact on the foot than it is designed to withstand, leading to specific injury.
Well, that's not what the study says. From the page linked above, a graph showing the impact when landing with a heel strike in a running shoe: