On Saturday, Apple announced its iTunes App Store had reached a new milestone: 10 billion app downloads. The 10 billionth app was downloaded by Gail Davis, a resident of Orpington, Kent, U.K. She won a promotional contest Apple hosted to celebrate this event, and is now the lucky winner of a $10,000 iTunes Gift card. Her kids are thrilled, no doubt, considering it was actually their download that led to the win.

As Apple noted in its press release about the event, the rate of application downloads has been surging in recent months. Of those 10 billion apps, 7 billion were downloaded in the past year alone. That's an incredible number. And even more incredible is the fact that this mobile app growth trend is showing no signs of stopping.

A funny side note to this story: Davis initially hung up on Apple, thinking the phone call was a prank. But Apple called back, thankfully, and things have been resolved. She's thinking she may even buy an app-capable iPod, to join in the fun her kids have been having until now. Her old one only played music. How's that for irony?

But back to the topic at hand: billions and billions of app downloads.

Explosive Growth

The iTunes App Store now offers over 350,000 apps to more than 160 million iPhone, iPod Touch and iPad devices in 90 countries around the world. It's the de facto standard as to what an app store should look like, how one should function, and it has resulted in the creation of an industry of competitors, from Google's Android Market to RIM's BlackBerry AppWorld and more. There are even "app stores" popping up for non-mobile platforms these days, leading to what some are calling the "appification" of the Web, or, more ominously, the Web's death.

There are app stores for game consoles, desktop computers, and for enterprise software. There are even app stores within apps, such as the one that popped up in bitTorrent client uTorrent last spring. And there are app stores for apps, like oneforty, the unofficial Twitter app store, or the app store for Foursquare, hosted right on the company website. There are app stores for TVs, for cars and for printers. Simply put, apps are everywhere.

Incredibly, this "apps for everything" trend is continuing, and at a rapid pace. Will it ever reach a plateau, we wonder?

Apple's Apps More Popular than Music

Last week, we cited recent research from mobile analyst Horace Dediu of asymco, where he found that apps were to reach the 10 billion download point in less than half the time as it took songs on iTunes. Of course, many apps are free, while songs are not. But that statistic alone doesn't account for this type of growth: 30 million downloads per day, says Dediu. And growing still.

Other recent analyst forecasts, this time from World Mobile Applications Market, have stated that the app store marketplace will reach $25 billion by 2015. This confirms the worldwide growth trend of apps and the associated app store marketplaces.

With such an app explosion on our hands, what's needed now are more services that help to filter, recommend, rate, review and surface those apps. No person on their own can sift through an ecosystem where hundreds of thousands of apps reside in order to find the best ones. Expect to see more application search engines and recommendation sites in the coming months and to see those that currently exist grow in popularity.