The PS3 version of Modern Warfare 2 has been struck with a series of leaderboard hacks that see cheaters appearing at the top of the lists with impossible figures.
According to reports, the PS3 leaderboards are showing hackers sitting high on the rankings with statistics simply not achievable (showing play time to be in the tens of thousands of days, for example).
A quick Google search brings up all sorts of foul play techniques people are employing just to see their names at the top of the listings on PS3, presumably because they're too rubbish to place high using actual skill.
We've asked Activision how it tends to fix the problem, hoping it won't call for a full leaderboard reset. Needless to say, we expect the people with the power to break out the Hammer of Bannage on those who cheat. So you probably shouldn't.