They actually have skin in the game (dollars).

7Eleven soda cup poll has Obama 70-30 (57-43 in Ohio) and they have never been even 1% off the mark.

I don't even bother reading all of the poll hysteria here on DU.

they are an offshore gambling operation, and that they also predicted Obamacare would not make it past the Supremes.

I've found they tend to track Nate Silver's 538....

It's not a traditional bookmaking operation where a bookie sets the odds and everyone makes a bet and waits for the event for a payoff. Instead, it's a supply-and-demand driven marketplace where the price is set what the users are willing to accept to buy and sell shares. Additionally, you don't have to wait until the event is over once you've made a bet - you can lock in a profit or loss at any time by selling your shares at the current price. This lets the price flexibly react to events, as well as changes in the polls, and there are plenty of people on Intrade looking to make money on the movement of the priceline as well as on the final outcome.

Since Silver is the go-to-guy for polling math, the smart money will want to lay his odds, and any time the Intrade price is out of step with his prediction, speculators will put pressure on the price until it converges near his estimate. He could probably make a fucking mint on Intrade if he didn't have to worry about it killing his professional reputation.

I also just discovered that "Will Obama be elected" and "Will Romney be elected" are separate events, each of which you can bet for or against. So there is guaranteed to be arbitrage activity that will push both sides to a natural convergence point.