It's hard to make really significant money on InTrade. I don't think you could make a living at it, for example - there's not enough liquidity.
There were some fun opportunities to arbitrage InTrade against BetFair this election, if you could be bothered with the faff of setting up an account on both of them. InTrade had Obama at 66-66% for a while, whereas BetFair had Obama at 79-80%. You could buy on InTrade and hedge on BetFair, and make a guaranteed profit (even after t-costs).
The presidential market on InTrade was quite liquid. $300k of volume with a bid-ask spread of like 0.2%.
Do you know why there was such a persistent gap for arbitrage between InTrade and BetFair? I don't know about BetFair's vig and rules, but InTrade has only a couple of small fixed transaction costs. ($5/mo to have an account and $10 to pull your money out, I think.) Seems like it should have been eaten up.
There were some fun opportunities to arbitrage InTrade against BetFair this election, if you could be bothered with the faff of setting up an account on both of them. InTrade had Obama at 66-66% for a while, whereas BetFair had Obama at 79-80%. You could buy on InTrade and hedge on BetFair, and make a guaranteed profit (even after t-costs).