Spent half an hour or so reading about it this morning. The premise seems to be using free bets with bookies to back an outcome and then laying the same bet at Betfair or someplace similar. Results in guaranteed small victories which build up over time.
Seems as though if you're willing to spend a bit of time figuring it out and an hour or so a day on it you can treat it like a part time job and earnings of £300-£500 a month are apparently not difficult as long as you have the discipline to stick to the principles of doing it.
Couple of links below that I'm going to read up on today. Anyone here have any experience with it already?
http://www.jamie-anderson.com/profit-accumulator-review/
http://www.profitaccumulator.co.uk/