Read this on another forum
No idea how much truth is in this , If your laying
horse books tread carefully
You have £200 in your account. The software lays all runners to a 101% book. You now have £200 back in you account to lay the runners again. You can repeat this process as quickly as you wish. BUT the software does not take into account reduction factors. Recently it was witnessed, not for the first time, a race where one of the horses was a known non runner, doubtful runner, so Betfair set its reduction factor to 0%. So when the non runner was taken out, instead of making a lot of 1% profits the software, with a mere £200 in their account the user lost
£40,000.