This is why we can't have nice things. A Russian hacker who goes by ZonD80 has published a way to (using his servers) bypass the actual App Store's in-app purchasing servers and unlock content without having to pay. While slightly clever, this is bad for a few reasons.
First, you're stealing. That's bad enough, but should you need more it's important to note that you'll also be sending a Russian hacker info like the unique ID for your device. As much as you want those billion Smurfberries for free, we recommend you stay far away from this. Here's hoping Apple patches this quickly.
9to5Mac has more details (via i-ekb.ru) but Macworld interviewed the hacker and a few developers for response. Also, commenters on 9to5 point out developers can (and should) validate receipts, which is how some apps are able to deny would-be thieves. I'm guessing many more developers will implement this now.