To be fair, it is selling. They've sold less than 100,000 units, they say, and even half of that is a nice chunk of sales. But apparently that's not a success, and they're wondering why. Piracy is their first guess -- we've heard before that piracy can be a huge issue, even on cheap apps. They say the game had an 80% piracy rate in the first week, which has since dropped down to 24%. I'm not convinced piracy can be blamed completely -- there's no guaranteeing that all pirates would have bought a real copy anyway.
But certainly there's something going on here -- you can have a terrific app that's well-reviewed and buzzworthy, and if it doesn't end up in the right place at the right time, it still won't be successful (or at least as successful as you want). Everyone is still working to unlock success in the App Store, but with over 100,000 products on the shelves, it has become increasingly more difficult for the good apps to stand apart.