(Corrects price of Fatify app)

Who says America doesn’t innovate? The iTunes store offers more than half a billion apps, and the camera category has split into dozens of sub-branches. Hit the right magical mix of photo features and you, like Instagram, might get $1 billion from Facebook.

Data: App Annie. Double-click to zoom. Click to drag. Press 'H' to show all. Right-click for more options.