The App Store had its billionth download today — nine months after its launch. This is remarkable by any measure. And as Apple and AT&T posted their earnings in recent days, it was the iPhone that saved the bottom line for both of them, even giving Apple a record profit at a time when Mac sales are down. So who won? And what was the billionth app to be downloaded? The contest page hasn't yet posted the results as I write this. It simply says, "Thanks a billion," and invites readers to check back to see the winners.