Insoo doesn't even have to take the phone out of his pocket to send an SMS. He knows how to slide it open, which buttons to push how many times to reach the "Send SMS" menu option, compose the entire text message, and hit the send button -- all without even looking at the phone.
For advertisers, push notifications are much cheaper than SMS notifications, which are marked up to pennies a minute by carriers and network middlemen.
Push notifications via the Facebook phone would be able to undercut the prices of virtually any SMS notification while providing advertisers access to a highly desirable demographic.