People always think that getting a Doctors opinion about say, vitamin D, is the safe route to go. I tell you it's bull. The least informed person on this board probably knows more than Doctors.
Yes I know... MD don't know anything, we're all so much brigther than they are right? It's much better to listen to someone on a forum over the internet than to have a doctor (who usually has a solid understanding of biochemistry and biopathology) following you with test in an adequate clinical setting. MD are all idiots that know nothing about health else than what Pharma is telling 'em.
It's scary to see that this "internet easy-information-acess" phenomenom has gotten people to think they know much better than an MD. Yes, some are pretty bad, like in any profession, hence why i've added (good) doctor. But to say that the person who knows the least on this board probably know much than most doctor... lol...
I strongly disagree with this. It is not about any one doc being bad, its about the MD being a generalist, having to know all the basics on such a vastly deep subject. I would put this forums resources, with the ability to search, and probably more importantly ask questions, above 999/1000 doctors advice. But this forum (and more specifically this subforum) is dedicated to a very narrow slice of what comprises all of medical knowledge. So taking into consideration the gargantuan amount of information available pertaining to just this slice of ours, it is not arrogant to believe this will be a more current and up to date resource than an MD who learnt about it at university years prior. There is also something major to be said for many self-taught experts, who often have unique perspectives due to not going through the regular system to obtain their knowledge (low fat anyone?).
Case in point: In the "What blood tests should I do?" thread currently going there around 10 or so tests available that everyone seems to agree are the best blood tests for checking your overall health. Now if you had to chose between the hypothetical top 99.999% 1 out of 1000 doctor I stated above interpreting your results or a thread on ImmInst where a discussion took place and a few of the 'heavy weights' chimed in, which would you chose? For me its no choice 
I agree with many things you say, i'll just make sure that my stance is clear. MD have a very solid understanding of the human body (neurology, immunology, musulo-squelletal, biochemistry, biopathology, etc, etc.) As such, they know many more
whys than someone like me, who has a very limited knowledge about the human body. Also, they are much more easily able to undertand a specific information since they have a solid understanding of the basic, something I cannot easily do. Usually when I learned something specific (such as what is discussed on forum like this) I've got to dig back to the basic to understand why it is like this. Also, they are more likely to make links between different phenomenom much more easily than again, someone like me. They can understand the mechanistic behind something much more easily than I can.
When you want to have yourself a new house, do you start reading on house building and then feel like you could
teach the contractor how to do his job? If you need a lawyer do you start studying law and feel like you could represent yourself in a court? It's all good to be an autodidacte, but it's foolish to think that MD don't know much and that simply by reading you can overcome a universitary degree, that is well planned and programmed to make sure you learn everything that you need to do your job.
Yes, they have a lot to learn, and no they cannot learn everything, but assuming that they don't know much and are all retarted is... well I don't know, foolish probably.
Personnally, I think humility is a good things, and i'm not gonna start feeling superior to someone who has a degree in medecine because I read blogs, forums, and few studies here and there.
My basic understand of the human being is far from being equivalent to what a MD has, and I know they understand much more than I do, even if it's not as specific as what I sometime get.