Daring Fireball is spot on:
The conventional wisdom at the moment seems to be that the iPhone is only a consumer device, but the conventional wisdom is wrong. Think about all the hospital/medical demos from recent iPhone events, for one thing.
We've said for a while here that enterprise and business aren't constrained to sales forces and corporate messengers. Hospitals are big. Schools are big. Entertainment is BIG. The iPhone, especially with iPhone OS 3.0 and the iPhone 3.0 SDK are formidable tools for deploying mobile devices and applications in a wider range of businesses than perhaps anything previously put on the market.
Wall Street might stay with messengers -- every job has its best tool -- but while Main Street is considering iPhones, and a lot of businesses on every other street might just be as well.
Check out the 80+ page iPhone OS Enterprise Deployment Guide PDF via Apple.com