Braussie: +1, alread own so not redeemed :) Thanks! Best wishes to the Ninjas!
johnki: I've always wondered if some lucky ninja grabbed one of the "false" keys without reading that there was a letter/number that needed changed and ended up getting a different game...
I would think the chances are very slim, since I think there's 36^15 possibilities for the 3 set, 5 character codes like you posted. But it's possible. If my calculations are right, there would be over 221,073,920,000,000,000,000,000 key combinations, or redeemable codes. But hey, it could happen :) - Especially when you consider how many copies of each game there are.
Then there are the really long codes that have 5 sets of characters or more. :)
I wouldn't mind accidently getting Castle Crashers or something when trying to redeem a game, lol...