Yes, Facebook is about to launch a mobile platform aimed squarely at working on the iPhone (and iPad). But it won’t be distributed through the App Store as a native application, it will be entirely HTML5-based and work in Safari. Why? Because it’s the one area of the device that Facebook will be able to control (or mostly control).
Facebook will never admit this, but those familiar with the project believe the intention is very clear: to use Apple’s own devices against them to break the stranglehold they have on mobile app distribution. With nearly 700 million users, Facebook is certainly in the position to challenge the almighty App Store distribution mechanism. But they need to be able to do so on Apple’s devices which make up a key chunk of the market.