Also, some food for thought. The rule of thirds makes perfect sense as a point of physiology. I treat people with balance disorders: vertigo and imbalance. How we use our eyes to look at the world is hard wired. About 1 /4 of our brain, the cerebellum, has no other function but to integrate information from our ear, eyes and from the tug of gravity on our body so that we can stay upright and function normally in space. Significant amounts of our brain besides the cerebellum are also dedicated to our balance system. Our perception of the horizon is a major part of our balance system. We naturally divide the horizon roughly into thirds, foreground, mid ground and distant. The rule of thirds is part of the hard wired balance system that allows us to walk upright, as well as part of the balance system for most vertebrates.

For people with balance problems, if you take that visual perspective away, such as in the dark or going from Sun to shade or when entering a long hallway, the sense of imbalance can be overwhelming. As upright animals, the prime intent of our eye movement is to provide information to our balance system so that we can maintain our upright position, walk, track objects, and rapidly perceive danger requiring us to move quickly. Given that we are hard wired to look at the world in thirds, the rule of thirds in photography is not surprising.

Also, some food for thought. The rule of thirds makes perfect sense as a point of physiology. I treat people with balance disorders: vertigo and imbalance. How we use our eyes to look at the world is hard wired. About 1 /4 of our brain, the cerebellum, has no other function but to integrate information from our ear, eyes and from the tug of gravity on our body so that we can stay upright and function normally in space. Significant amounts of our brain besides the cerebellum are also dedicated to our balance system. Our perception of the horizon is a major part of our balance system. We naturally divide the horizon roughly into thirds, foreground, mid ground and distant. The rule of thirds is part of the hard wired balance system that allows us to walk upright, as well as part of the balance system for most vertebrates.

For people with balance problems, if you take that visual perspective away, such as in the dark or going from Sun to shade or when entering a long hallway, the sense of imbalance can be overwhelming. As upright animals, the prime intent of our eye movement is to provide information to our balance system so that we can maintain our upright position, walk, track objects, and rapidly perceive danger requiring us to move quickly. Given that we are hard wired to look at the world in thirds, the rule of thirds in photography is not surprising.

Let me start by saying kudos for a terrific post and subject, and one that many can benefit by. As for my thoughts on the subject I believe in the rules or guidelines, and use and adherence to them does, and will make a difference in one's work. And there's nothing new about them having been used and developed by the masters over the centuries, and who am I to say "they should be broken." I think we have three schools of shooters to consider, and maybe some would fit into all three categories of them. One, you have the photographer who wants to create art in their work, and the rules mean a lot to those folks. Then you have the casual shooter who's mostly interested in some memory shots of the family, or the places they visited. And maybe for those folks a tree branch "growing" out of their granddaughter's head is less of a problem, it's all about capturing that moment and having it to cling to. And, lastly, the photojournalistic photographer where the photo is all about impact, and the rules are often not even considered. I think a good example of that would be that classic Vietnam era photo of that little Vietnamese girl running and crying with much of her clothing burned off from napalm. I'd doubt if that photographer was too concerned about the rules when he shot that. But, the impact will be long remembered.
The rules of design and composition are just a part of it, but a good part, IMO. You might add some subsets about some of the guidelines about the types and styles of lighting used, portrait do's and don'ts like where to crop, and where not to crop, or just where and how to place the hands in a portrait. Books with full chapters are written about these things. But, when it comes to the category one folks mentioned above all of these things become important, and can be a wonderful study. And it's all what makes photography the interesting subject that it is. And in this shot below I knowingly broke a few of the rules. :)