About Betting Exchange

Following http://en.wikipedia.org/wiki/Betting_exchange
"...A betting exchange is an entity which provides "trading" facilities for retail or bookmaker customers to buy and sell contracts. Contracts are structured as binary options. Some betting exchanges may also offer CFD products. Betting exchanges trade heavily horse racing and sports markets, but also include elections and current events markets..."
For a purpose of my research I use Betfair, currently the only one betting exchange in the world with liquidity being high enough to allow for analysing market efficiencies. The others include SmarketsBetdaqWBX.