I think the point is that it's not like Facebook; with facebook, you, the user, are the product. With app.net, the platform is the product, and you pay for it.
Facebook makes decisions about its system based on maximizing its ad revenue, not maximizing your ability to do the things you want with it. A product not relying on advertising can focus entirely on the users, ideally.
People scream about paying 0.99 for an app on the App Store yet App.net thinks all of the free-chasers are going to want to pay for yet another social network and one that has no ubiquity? Good luck to them.
Facebook makes decisions about its system based on maximizing its ad revenue, not maximizing your ability to do the things you want with it. A product not relying on advertising can focus entirely on the users, ideally.