@Brian: Apple doesnt care. Mobile messaging is about more than just business. Not everyone needs a full-featured collaboration solution, but most non-techies need a useable solution. What the iPhone offers is simplicity. It's not a business devices and that probably makes it a more useful solution to more people.
All of the muddle that goes into the typical business solution makes it about as easy to use as the average 10-person business meeting is productive. IMO, messaging and "collaboration" has become the scourge of productivity and is now the biggest distraction in the workplace. Think of "full featured" in terms of diminished capacity and the iPhone's offering in terms of useful simplicity.