Mobile Crunch is reporting the 10Billionth iPhone download will be soon and the Apple will give the person who does it $10K. Well, we got out our caculators and worked out when that will happen. We've worked out that Appstore is doing 280 downloads per second and on the 14th Jan MobileCrunch said it had done 976,64,36,797 downloads; so based on that information we reckon in 9.6 days after that reading it will go through to 10Billion. So if that reading was on the 14th then it will be on 23rd sometime.
See phonecount.com for the counter we use to do these estimates.