There's some sort of point about experts in general which I am not sure exactly how to articulate but I think is relevant. I'm going to try to klutz through it anyway.
There are lots of fields where fundamental theories are relatively weak or have poor predictive powers. Macroeconomics, climatology, nutrition etc. Basically, we don't have real Knowledge. We have a bunch of data and a bunch of theories. Some of the theories that aren't very general or aren't very applicable to real life scenarios are predictive but relatively useless. We know that certain nutrients have some importance. We know that restricting caloric intake leads to weight loss. We know that money supply, inflation and other things are linked together in various ways. The theories don't answer the questions we want then to with any kind of certainty. Still, we sometimes need to make decisions and some knowledge is better than none so we go and find experts anyway. There are people who are experts. They're experts in the study and they are aware of our knowledge in the field such as it is. But they don't have real answers because there just aren't useful answers to be had at this point. All of medicine was like this until pretty recently.
When Darwin published "The Origin of Species" evolutionary biology came to being as a different kind of field. One where the knowledge was real and the theory predictive. The theory was fundamental and strong. Darwin could make claims & predictions with a lot of confidence. Subsequent biologists could keep making predictions and when new discoveries (like genetics) were made, they were found to be consistent with the predictions of evolutionary biology. In fact, if they hadn't been, a careful researcher would probably assume that the mistake was in their own conclusions, not in Darwins. So if Chimpanzees are closer to humans than to Gorillas, we share common acceptors not shared with Gorillas and the distinction between Humans and Apes (if we want to keep Apes as a category) is morphological (which is allowed by Darwin) rather than one of proximity on a family tree.
Darwin was careful. He didn't publish until he was sure. If he didn't been sure we wouldn't have published. There are lots of Darwins in every one of the former type of field. They haven't discovered real Knowledge that can tell them what to do in an economic recession or what people should eat so they shut their mouth and keep looking. They are still experts but their expert opinion is "I dunno." That doesn't register as expertise so we go on to find someone that will explain about Aggregate demand, antinflamatory diets, carbohydrates or something like that.
Development methodologies, executive compensation, distributed companies etc. are in the category of things that we don't have real "scientific" knowledge about. Most business-ey knowledge is like that.
Now it sounds like I'm bashing people who talk about this stuff and I don't mean to be (hence my disclaimer at the start). I'm just pointing out that our knowledge in different fields is different. Joel Spolsky is very insightful in his essays about the Software industry, for example. But there are certain people that are comfortable with anecdote and generalities and assertions that may turn out to be untrue. There are certain people (like Darwin) who are not. If we're talking about development methodologies, the people we here from are self selected. They are comfortable making grand statements, manifestos and such even though they may be wrong.
That's still useful and certainly interesting, but there is a big category of people we aren't hearing from and they are relevant to the discussion.