Betting arbitrage, miraclebets, surebets, sports arbitraging is a particular case of arbitrage arising on betting markets due to either bookmakers' different opinions on event outcomes or plain errors. When conditions allow, by placing one bet per each outcome with different betting companies, the bettor can make a profit regardless of the outcome. In the bettors' slang an arbitrage is often referred to as an arb; people who use arbitrage are called arbers. A typical arb is around 2 percent, often less; however 4-5 percent profit is occasionally obtained, and sometimes even 20 percent. Arbitrage betting involves relatively large sums of money (stakes are bigger than in normal betting), due to large sums of money being required to generate a decent profit. It is usually detected quickly by bookmakers. Arbitrage betting is almost always insufficiently profitable due to detection, hackers, unreliable betting websites, limiting of stakes, and the use of high percentage arb's to con arbitrage bettors into giving security details.
I've been using an Arb Alert service for a few months now and I've been greatly impressed. Here is my genuine feedback though:
1) You need to know your websites. I've been laying a lot of bets at Smarkets. Smarkets sometimes makes it hard to see if your bet has went through or not. This has meant that on one occasion I clicked the "confirm bet" twice and lost £60.
2) Don't use the auto bet option in the Arb Alert software. I've found it cumbersome. I prefer to open the bookmakers windows myself.
3) Be aware of stake limits. Some of the online Bookmakers have extremely low limits. Today I was limited to a £20 bet on an English Premier League o/u bet!