In the world of running technique, there is a lot of needless emotional and immature quibbling over which technique or theory is the best. This bickering at times gets quite personal, and it seems as though many people cannot accept that it is possible (and okay) for people to have an honest difference of opinion based on known facts. There are gaps in our knowledge about this subject, so it is inevitable that people will fill in those gaps differently.
It occurs to me that part of the problem is that people often think that they are discussing the same thing, but aren't. For example on one of my favorite blogs, Runblogger, there was a discussion several months ago on how the foot strikes the ground. I was stunned when I realized that most people seemed to define landing as the moment the foot touches the ground. My working definition for landing was, and continues to be, when the body's center of mass is no longer descending. Both definitions are perfectly legitimate, but they do not mean the same thing.
If you define landing as the moment the foot touches the ground, then it is probably impossible to "land" underneath your center of gravity. If you define landing as the moment the center of mass stops descending, then it is definitely possible to "land" underneath your center of gravity. An analogy might be defining when an airplane has landed. Is it at the first touch of rubber to the landing strip, or when the full weight of the plane is on the ground? There is not necessarily a right answer, but I think of a plane as having landed when its weight is fully on the ground.
Imagine two people discussing running technique using the word "landing" with completely different ideas about what entails a "landing". It is easy to see how these people could walk away from the discussion thinking that the other person doesn't know what they are talking about. When it comes to running technique, there is more agreement, than disagreement on what constitutes good technique. There are differences worthy of mature and fact-based discussion, but I'm becoming more and more convinced that many of the debates on this subject are based more on semantics than they are on physics.
For more information:
A link to the discussion I referenced on Runblogger - http://www.runblogger.com/2010/08/on-running-form-ii-where-should.html