With all the noise that Apple is making about having over a billion apps downloaded from the App Store, you would think users everywhere with iPods and iPhones are downloading apps like there is no tomorrow. After all, one BILLION is kinda mostly a ginormous number. However, a report put out by AdMob, one of the leading ad platforms for the iPhone, suggests that this is not the case. Their internal metrics show that out of the 2300 applications they track (the ones that their platform is on), only 5% of those, or 116 applications, are used by more than 100,000 “active users,” whom they define as people who use the application at least once a month.

On the other hand, 54% of the apps have less than 1000 active users. If this trend was extended to the entire app store, then, the ability to monetize an iPhone app may be overstated by Apple. Most of the apps (whether they make money by advertising or otherwise) depend on achieving some critical mass, and if only 5% of apps are actually seeing that, the other 95% are probably not that profitable.

However, Techcrunch points out that the vast majority of the apps tracked by AdMob are free, so the statistics are not indicative of the whole. Also, this doesn’t account for actual number of downloads, as there are probably several users who download the app, use it once, and delete it, which is still troubling for developers that depend upon ad revenue, but not as much for those pocketing the change from a paid download.

Another interesting statistic from the same AdMob report is that iPod touch users are updating to OS 3.0 at a far slower pace than iPhone users, presumably because of the $10 upgrade fee. They present statistics that show that 3.0 represented 44% of iPhone ad requests five days after its launch, as opposed to only 1% of iPod ad requests. This won’t hurt Apple, necessarily, because they make most of their money on the sale of the actual hardware, but both hurts their image as well as developers who are switching their apps over to 3.0, and won’t be able to reach the disenfranchised iPod owners.