I totally agree with the comment "the bookie always wins". Fortunately, if you get your head around betfair you can actually be a bookie, by taking bets yourself and off-setting them aswell. It took a while to understand it (with the help of a proffesional gambler) but it can pay off. You also need a good understanding of horse racing and exploiting poor odds / good odds on any betting spectable.
I did lose a lot on Saturday, but since 05/04/08 Im in the black. Its not life changing but its more than enough to loose £11 grand on any given day. 2 weeks of daily losses like that Id quit, but the odds are so far in your favour it is very unlikely to happen.
Paul