One thing you have to watch out for on Intrade-Betfair arbitrage is the not insignificant risk of not doing the trades you think you're doing. I know Intrade h

One thing you have to watch out for on Intrade-Betfair arbitrage is the not insignificant risk of not doing the trades you think you're doing. I know Intrade has rules that various events will cause trades to be stopped and completed trades will be undone. Betfair might as well, but the two markets don't have any synchronization on when or why. Since you'll constantly have many times what you expect to gain in a day at risk on the markets, a single rollback event could put you very deep in the red.