Sales of the iPhone for the current quarter may be down, but sales for the decade are up, way up. Apple last week announced that it had sold its billionth iPhone, a historic feat for a consumer electronics product from a single vendor. "We never set out to make the most, but we've always set out to make the best products that make a difference," said Apple CEO Tim Cook. "iPhone has become one of the most important, world-changing and successful products in history. It's become more than a constant companion."