Smartphones used to be the domain of supergeeks and tech professionals – people who needed or desperately wanted the functionality of a full computer in a tidy mobile platform. As the devices became more popular and the desire for on-the-go web capabilities grew you could almost smell the storm coming.

Then the iPhone came out and sold millions, spurring competitors to make their own touchscreen wonderphone. We’ve now got the Blackberry Storm, the HTC G1, the Palm Pre, the Nokia N97, and the Samsung Jet, all running on a different operating system. While the manufacturers tout the hardware features that make their phone the best (physical keyboards, a screen that clicks, a camera with a flash), consumers are starting to look to the software that runs the phone, and the applications they’re finally able to install, to make a decision.

Apple has been most successful with third party application sales and support due to their App Store, which opened in mid-July, 2008. Since release, the App Store has seen more than a billion application downloads and now showcases more than 50,000 third party applications. From games to translators, finance tools to ereaders, the Apple App Store has an app for almost anything, leaving its competitors lagging far behind.

It’s taken nearly a year for competitors to get their mobile application stores up and running, time during which Apple has continued to lure consumers with the promise of a robust app catalog. As Business Insider points out, consumers aren’t just investing in a phone, they’re investing in a platform, with application quality and quantity as a major component of that investment. In a similar article, BI adds that time users spend with applications is replacing time spent on the web. Apps like Yelp allow users quick access to restaurant reviews, where before they would have been using Google.

This isn’t just good news for Apple, it’s an important statistic for developers. As more and more users turn to applications, developers are making decisions about which platforms to support, and which to ignore. Though there’s no direct competitor to Apple’s App Store, other platforms have made a decent start. Google’s Android, for instance, has nearly 5,000 applications, which puts them at a 5:1 advantage over their closest competitors, Nokia and RIM’s Blackberry. Palm, which launched the Pre in early June, has a meager 30.

As I mentioned earlier, though, it’s not just quantity that counts, so Palm may not be out of the race. Application stores are continually adding features, like the ability to recommend apps to friends. The best apps are sure to see increased traffic as it gets easier to share your favorites.

There’s also ease of development to consider. Developer support for the iPhone has been mostly good, though the application approval process can be a bit unclear, which could frustrate some developers away from the platform. WebOS, which runs the Palm Pre, is based on web technologies like Java and HTML, meaning developers already know how to write for the phone. They just need access to the SDK.

Lastly, developers have to think about upgrade paths. While WebOS may offer a familiar development language, what will the upgrade path look like in 3 years? Will the next WebOS break current applications? Will WebOS still be around? I would love to say yes, but it’s hard to bank on something like that when WebOS is a first-of-its-kind OS from Palm. They may reverse their thinking on the platform come their next major hardware release.

However young, the application marketplace is extremely volatile, and it will have an ever greater effect on consumer choice as store offerings grow. Can the Palm App Catalog keep the Pre alive and well? Is Windows Marketplace a mistake? Is Android the way of the future? I’ll be following all the latest developments here, so be sure to check back often.