Interesting Steve quote from Q&A:

    We don’t know much about the advertising stuff. We’re
    learning. We tried to buy a company called AdMob, the
    biggest mobile advertising company. But Google came
    in and snatched them from us. They didn’t want us to 
    have them. So we bought another smaller company, 
    Quattro Wireless. They are teaching us. But we are 
    babes in the woods. We are learning as fast as we can.

edit: Mostly referring to the 'babe in the woods' comment, along with his perspective on the AdMob purchase.