Arbitrage betting should not even be possible, as it means taking advantage of the differences in odds offered by different sites and there is nothing wrong with that. Any good bookmaker will have very similar odds to every other sportsbook and they can actually price their odds to help themselves. If they take a big bet on one side but later decide the odds have changed and are unfavorable to them based on new information, they may decide they want to balance their risk by offering favorable odds in the opposite direction. Either way, it is not something they would be that bothered by if they have priced odds based on calculated analysis based on data mining.