The first billion downloads form the store took took nine months, with that milestone being achieved in April 2009. With a growing number of devices in use, the second billion was notched up just five months later in September 2009.
The third billion took a little over three months.
"Three billion applications downloaded in less than 18 months — this is like nothing we've ever seen before," said Apple CEO Steve Jobs.
In an apparent dig at Google's Android platform, he added "The revolutionary App Store offers iPhone and iPod touch users an experience unlike anything else available on other mobile devices, and we see no signs of the competition catching up anytime soon."
Apple gave no hints about what proportion of the three billion downloads were free or paid.
The App Store hasn't been free of controversy, with some developers expressing concerns about the approval process. Some people also object to the idea of a single source for third-party software (especially as Apple takes a reportedly non-negotiable 30% commission on all sales), or the fact that Apple has built in a 'kill switch' allowing any particular application to be remotely disabled en masse.
It was a hot Christmas at the App Store - find out just how hot on page 2.
Mobile analytics firm Flurry recently reported a surge in app downloads during December 2009, which it ascribed to a large number of iPod touches and iTunes gift cards being given as Christmas presents.
iPod touch downloads were 172% higher than iPhone downloads on December 25, and nearly 1000% (yes, ten times) higher than the average for previous Fridays that month.
iPhone downloads rose by over 900% on Christmas Day.
The acceleration in download numbers shown in Apple's broad-brush announcements is also reflected in Flurry's more finely grained numbers. It reported record download volumes in November 2009 (15% higher than in October), followed by a huge 51% growth in December 2009.
In comparison, Android Market downloads grew by 22% from November to December 2009, with the Droid accounting for almost half the volume.
Flurry officials previously described the iPod touch as Apple's weapon of mass consumption with long-term strategic value to the company: "When today's young iPod Touch users age by five years, they will already have iTunes accounts, saved personal contacts to their iPod Touch devices, purchased hundreds of apps and songs, and mastered the iPhone OS user interface. This translates into loyalty and switching costs, allowing Apple to seamlessly 'graduate' young users from the iPod Touch to the iPhone," said Peter Farago, vice president, marketing at Flurry.