This guy got away with it for 5 years. The only other one I know of is the McDonald's Monopoly guy who rigged it for 4 years. This tells me you can get away with it for a while, repeatedly. And I really doubt most people would take a huge payout, then keep working that job to do it again. So I suspect that it takes 4 or 5 years to get caught and we're just catching the minority of people greedy enough to keep their scam going for years, despite the massive amounts of money they've accumulated already.

Let's start the betting on the answers...