The fix is in (the genes?): why a love of risk may lead some athletes astray
There are many causes of match-fixing but could some athletes, by their very nature, be more susceptible to the lure of fixing sporting events?
I would think the element of risk involved may well play a part, but I think bigger incentive is probably just money - especially with these lower league teams you hear about who are all in on it.
The article starts on the subject of Stephen Lee as well, news that broke in the last week or so regarding his match fixing scandal, with fuel added to the fire by Ronnie O'Sullivan when he said along the lines of how match fixing was much bigger than was reported and everyone's on the take.
EDIT: also a boat load of extra links regarding the last week's match fixing scandals - apparently there was an Aussie Football match fixing scandal as well as the Singapore and Stephen Lee items.