[ZeeJustin]

I also want to add that I can't think of a single case in my entire adult life where I had been told that "most the experts think Y", and my response wasn't either of the following:

"Well I guess Y must be true."

"There's a good chance you are wrong about most the experts thinking Y is true, but if you are right, then Y is probably true."

I guess I need to exclude poker from this, because I think I have enough knowledge in several areas of poker theory to reasonably disagree with even the most qualified experts.

Edit: That last paragraph I wrote made me think of something. Assuming that the A's are the top echelon, it might be rational for an A to think Y is false even after seeing the survey results, because it is possible he is better qualified than anyone else. But it is extremely unlikely that a B shouldn't change his mind after seeing the results of the survey, because it is unlikely that he is more qualified than the A's that disagree with him. G's should absolutely change their mind once hearing of the survey.

I think the answer to David's question is obviously, "Y is probably true even though 70% of A's disagree", but I think it is a lot more interesting if you instead ask, "You are an A. You were 95-98% confident that Y is false. Should you change your opinion after hearing the results of the survey?" I think the answer is probably yes more often than it is no.