"If there is one thing I learned by reading Epstein’s “The Sports Gene” it is that world-class athletes are, by definition, abnormal: that is, the kind of person capable of competing at that level is necessarily very different from the rest of us physiologically. They are outliers. In one of the posts on the running Web site LetsRun.com, someone recently commented that Mo Farah has, essentially, zero body fat. The poster meant that as evidence of something fishy with Farah. But you could just as easily say that the kind of person capable of being the greatest distance runner of his generation is necessarily NOT going to look like you and me. So Dibaba? It is not impossible that we are simply witnessing one of the greatest middle-distance runners of all time. Let’s just enjoy what we are seeing."
These analyses are pretty great. I gotta disagree on their point in the other article about the importance of form for new runners. When you're a four hour marathoner, form doesn't matter, heel striking is fine - get the miles in! You will adapt to an efficient form for your body type.