The in-app purchase feature that Apple added to the App Store long ago made it easier for the app makers to make money off the apps they sell. The in-app purchases let you buy things to add to your games and such. Pirates can steal apps and put them up on the web for people with jailbroken devices to get for free.
The thing with in-app purchases is if the game was free but they needed in-app purchases to operate or add items needed the pirates were foiled to some extent since they had to buy the add-ons to extend their game. UK developer Mobile Pie has claimed that the in-app purchase option for £26.99 on its My Star game had a 93% piracy rate in October.
The finger is pointed at a new hack tool called iAP Cracker. The iAP Cracker lets pirates game the system and presents a really issue for devs that have relied on in-app payments for their income. Mobile Pie creative director Will Luton has offered a link to a website that shows how iAP Cracker works and then a link to a Google Doc spreadsheet showing the games that the hack affects.