AdMob, one of the world's largest mobile advertising networks, released its Download Exchange today. In return for running ads for other apps, developers can now promote their own apps across AdMob's network of over 1,000 applications. At its core, Download Exchange is basically a more sophisticated version of the many banner and link exchange services that are very common on the Web.
According to AdMob, developers will be able to target their ads by OS version, geography, and device (iPhone vs. iPod touch). AdMob will also assist developers with creating ads for their apps, and developers will be able to access download and monetization reports on AdMob's web site. Because some apps are obviously quite similar, developers will also be able to filter out apps from their competitors.
AdMob will allocate ad impressions based on the quantity and quality of the inventory that each member contributes.
Given that developers have relatively few outlets to promote their applications outside of Apple's App Store, this looks like a good way for developers to get the word about their applications out to users. Given that the ads appear in other apps, the targeted users are obviously already interested in downloading iPhone apps.