At Overcoming Bias, Eliezer Yudkowsky invites pundits, partisans, and anyone else with a nascent opinion about the limits of prediction markets to, in effect, put up or shut up. (Though he puts it in somewhat nicer words). Here is a selection, but read the whole thing:
If you think that Hillary is going to do better than the polls on Super Tuesday, and you’-re going to sneer afterward and say that Intrade was “-just tracking the polls”-, buy Hillary now.
If you think that Obama is going to do better than the polls on Super Tuesday, and you’-re going to gloat about how prediction markets didn’-t call this surprise in advance, buy Obama now.
The point is not that prediction markets are a good predictor but that they are the best predictor. …- If prediction markets react to polls, they’-re getting new information, that they didn’-t predict in advance, which happens. Being the best predictor doesn’-t make you omniscient.
Everyone’-s going to find it real easy to make a better prediction afterward, but if you think you can call it in advance, there’-s FREE MONEY GOING NOW.
Buy now, or forever hold your peace.