From SFE blog Spontaneous Order:

This clip demonstrates that perhaps a crowd of “uneducated” people will be better at predicting futures than the experts.  Intrade, a website which hosts a slue of future markets, has had impressive results.  Intrade hosts future markets which are valued between $0.00 and $1.00.  $0.00 = 0% while $1.00 = 100%.  Users of this website use real money and invest in futures ranging from politics to the predictions of the stock market.  An example of a market follows: A market for Barrack Obama to win the presidency was recently on the website.  If he were valued at $0.80, that means that the aggregation of people believe Obama has an 80% chance to win the election.  This would leave McCain at 20%.  Lets say I invest 100 shares in McCain.  If he ends up winning (which we now know is false), I would profit $0.80 per share.  It’s a neet utility that seems to have some useful applications.  Check it out!