A sure sign that Apple's iOS ecosystem is thriving, the 10th Billion app download milestone was reached today by the Apple App Store. Opening in July 2008, the App Store marked the legitimacy of the iPhone and iPod Touch as computing devices that could run multiple applications, barely 3 years later 10 Billion applications have made it to the 160 million iOS devices out there. The number one app in the store is still Angry Birds.