Don’t Just Build An App. Build A Mobile Business.

A quick note about business models. As he is an Admob guy, he is categorizing app business models to two main category

"Decide whether you’re providing a one time, high value experience that favors the pay-to-download model or if you plan to reach a large audience and continue to engage them over time, in which case an ad-supported model often makes more sense."

However, with easy mini-payment options (in-app purchases, cross-promotion between apps) mobile is currently strong a business model that is potentially much stronger than either of these: get a (large) audience and sell more stuff to them. It's working for games (half of the top grossing apps in App Store are freemium), it's working for navigation apps, I'm pretty sure that it will work for many other categories too.