It took Apple nine months of selling apps for their iPhone to crack the billionth download. A 13 year old named Connor Mulcahey from Weston (Connecticut) is credited with the one billionth download. The app he downloaded was 'Bump', a free contact information transfer app. Both the downloader and the downloaded app will receive benefits. Connor Mulcahey will get tens of thousands of Apple software and hardware and Bump Technologies (creators of 'Bump') will get a tremendous amount of publicity. Their website homepage currently sports whimsical line "The BumpTM heard round the world. Apple, thanks a billion!".
More at http://blog.wired.com/business/2009/04/billionth-iphon.html.