A former Microsoft engineer stole more than $10M from the company
news.yahoo.com
news.yahoo.com
Like it would seem to be a simple audit would discover that "Hey $10M more gift cards have been redeemed than were sold..."
He got greedy and got caught, I am sure it triggered some sort of loss prevention algorithm. Microsoft is not stupid and a $10M USD rebate would show up in a log somewhere and be read by a bot to flag it as suspicious.