Intrade is a futures market where people with insider knowledge can buy into a position. So if you know of a scandal for a political candidate that will cause him to withdraw, you can go buy up all the other candidates and make some money when he does. This will alter his price, becoming a predictor before the news actually comes out.

Additionally, there is the "put your money where your mouth is" aspect of it. While every candidate in the primaries, is announced as, "the next president of the United States", you can see who the people really think will win based on which futures they purchase.

The CIA effort is more like taking a whole lot of people, asking them to predict something and seeing who is good at it. There appears to be some manipulation of those guesses across the breadth of the crowd but it is not mentioned. In contrast to futures markets, the players in the CIA effort have no stake in the game.

Right, so one would expect something like Intrade or other prediction markets to leverage both the statistical "wisdom of crowds" and insider information to be even more accurate.

The GJP prediction market is pretty similar to how Intrade operated, but a head to head comparison is going to be very difficult inasmuch as a) Intrade has been shut down for like a year now; and b) Intrade's contracts overlapped only a little bit with the IARPA questions.