That is why we started http://www.fairlay.com
We think right now we have the best odds on the internet for world cup games an we only take 2% of the net winnings. In average that is only 1% on all bets.
The next big thing will be to completely decentralize the holding of the funds with technology like this: https://earlytemple.com:8181/ and decentralize the resolve process with something like this: https://www.realitykeys.com or a reputation based system.
However - because of peer to peer betting, and low transaction cost you ALREADY FIND THE BEST ODDS on fairlay.com. Wagering $100 costs you on average way less than a bag of popcorn...