The Government Accountability Office performed an audit on the "business expenses" of federal employees charged to government purchase cards (their version of credit cards) and, shocker, found that about half of the transactions were frivolous and unauthorized. The extent of abuse in spending outside set federal purchasing guidelines is evident in charges for things like lingerie, gambling, iPods, online dating services, and a Postal Service group partied with a $13,000 steak dinner washed down with 40 bottles of wine and fancy liquor.
While these charges, fueled by the taxpayers' dime, are a bit more alarming than non-government employees abusing the company card, I'm sure there are plenty of these patterns in private companies. The cards were given to employees with the intended purpose of improving bureaucratic efficiency — perhaps they thought there wouldn't be an audit on their spending habits, for the sake of efficiency.
Have you ever seen this type of misuse in practice or broken any expense-account type rules yourself?