From Apple's official website:
As of today, nearly 25 billion apps have been downloaded worldwide. Which is almost as amazing as the apps themselves. So we want to say thanks. Download the 25 billionth app, and you could win a US$10,000 App Store Gift Card.* Just visit the App Store and download your best app yet.
The 10k is only good for the App Store, iTunes and iBook Store, but hey... That's still good money, if ya ask me!
*Side note that ain't really got nothin' to do wit nothin': Y'all know I'm jumping on that iPhone 5 once it's released and has an Otterbox case available. Jumpin' ship on #teamHTC like a motha!**