Actually I think that Facebook is shooting for something completely different than the Amazon market. Amazon is trying to bring competition to the app-space where Facebook is attempting to subvert everything that's done on the phone. Amazon want to sell apps that will run on your phone. Facebook wants to give you apps that run inside of the Facebook app. Facebook wants to be to the iPhone sort of what ChromeOS is to the netbook. You turn on your phone, open up the Facebook shell and then run all your apps inside their framework, this approach is much more damaging to Apple than a competing market like Amazon is.