Apple App Store has seemingly tapped an endless fountain of success.

Tuesday morning Apple announced the largest app store ever shows no signs of slowing, having just surpassed three billion downloads by iPhone and iPod Touch users worldwide. Nine months ago it had reached one billion and three months ago it had reached two billion, but the pace at which apps fly from the store's shelves, so to speak, appears to be growing at a phenomenal rate, with a little help from the holidays.

"Three billion applications downloaded in less than 18 months—this is like nothing we’ve ever seen before," said Steve Jobs, Apple’s CEO. "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."

Because Google and other major Apple competitors are set to make big announcements later this week in Las Vegas, at the 2010 Consumer Electronics Show (CES), it is said that Apple will be trying to steal some of their thunder, as it has done in the past at MacWorld events. This year, however, MacWorld is not to take place in the same week as CES and Apple is not officially involved as it once was.

Of particular interest to Apple (and more than a little bit related to its announcement today) is that Google is expected to formally unveil the Nexus One, the latest HTC-designed iteration of an Android smartphone. What makes the Nexus One unique versus other Android phones is that Google has had its hand more involved in the phone's design, and the near-finished product is already receiving quite a bit of hype.

Stolen thunder or not, Google has quite the fight ahead if it seeks to compete with a smartphone that can spur one billion app downloads in just three months.