Ali Diab (pictured, right), AdMob’s VP of Product Management, said today at EconSM in San Francisco that there are currently five things that are working in mobile advertising: the iPhone, applications, Android, Webkit (a mobile web browser) and conversion.

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In particular, he called attention to conversion, which is a measurable event, such as a download or intention to buy. “Conversion is something we are keenly focused on – even more so than online.” He said something they’ve discovered is to help with iPhone application downloads is the company’s new advertising-based “iPhone Download Exchange,” which launched last month. The program allows application developers in AdMob’s ad network to allocate unused ad inventory to help each other drive application downloads. Diab: “We are experiencing a run-rate of 2.5 million downloads a month—and that’s using remnant advertising.”