[alberto_balsam]

There exists big sports betting exchanges like Betfair, where there isn't a "house" and where they don't really have an incentive to limit big winners. I have friends who make consistent profit from these sites - though it must be said they do ramp up the commission

[erfgh]

How do you know that they make a consistent profit? You take their word for it? Gamblers are notorious liars and are also known to keep very poor record of their bets.