I joined an arbitrage mailing list a few weeks ago just out of interest. I probably get between 3 and 5 emails a week with arbitrage opportunities but the profit % is generally only 2 or 3% (occassionally up to 5%). Various sports have been mentioned - the european X-country events were popular a few weeks ago as well as tennis and even soccer. The main problem I see with this type of betting is you need to have accounts with numerous different bookmakers with a reasonable amount of money in each (if you are only getting 2% profit you need to place quite large bets to make it worth your while) - also you will probably have to move money around a fair bit - each time you make a bet one account will win whilst the other will lose so you will probably have to move money to the losing account to be ready for the next opportunity.

Another thing you need to be very careful about is the different rules regarding retirements - particularly with tennis betting - some bookmakers cancel the bet if the first set is not completed whilst others only cancel if the match is cancelled before the first ball has been served. If you were arbitraging on a match where a player pulls out due to injury half way through the first set you could find that your winning bet was cancelled whilst your losing bet was not (and therefore you have lost a big chunk of money).

There are definitely lots of arbitrage possibilities between Betfair and the bookmakers but you have to remember to allow for the commission betfair takes in your calculations.

The best arbitrage occassional crops up on Betfair when the market% is less than 100% for a given market - if you are quick you can get on both sides and make a profit and you only pay the commission on that profit. In the last week I have seen this on a Tennis market and a World Cup Cricket (the upcoming NZvIndia match) - only made a few dollars on each one but it only took me 30 seconds so I guess thats not a bad rate of pay!

The best way to make decent money from this type of betting seems to be with Betfair when you believe the price is about to shorten on a particular event - if you back that team then you can lay them back at a lower price. For example the other night in the Kenya v Zimbabwe match when Kenya took the 5th Zim wicket you could still get $2.90 for Kenya to Win so I put on $200. By the end of the Zim innings Kenya had shortend to about $1.50 so I layed that $200 back (if I wasn't tired I probably would have let it ride and just layed it back if Kenya started to get into trouble but I wanted to go to bed so took the save option) - this left me in the position that if Kenya won I collected $280 profit and if they lost I came out even (of course I could have layed back more than $200 to ensure I won whatever the outcome but I was pretty sure Kenya was going to cruise home which they did).

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