I actually wanted to bet about $250.00 that Obama was going to win in 2012 on Intatrade, because I thought Nate Silver's models were more accurate then the market, but my wife really didn't want me to, heh. Still, there was a pretty big gap between the market (60% Obama or so) and the mathematical models (Nate Silver had Obama at over 90%; some other models were even higher).

On a more general note, I don't think the prediction markets in general were that accurate in 2012, because A: a lot of people were relying on provably false information, and B: I think a lot of people invested in the markets, not because they thought they knew the result, but because they wanted to manipulate the result (if the Intatrade market showed a close race, then the media might report on that, which might influence people's minds, ect).