A third way to distribute apps is Ad Hoc. The example given is a professor teaching how to develop iPhone apps in a class. Developers can be certified, then register 100 iPhones. Afterwards, apps can be thrown around in email and installed willy nilly as long as the phones installing them is part of the 100.
The Enterprise asked for a way to distribute phones that isn't accessible to other people in the world. They can distribute applications on their own intranet by first authorizing phones on their own network and then distributing it via iTunes.
The App Store will be available in 62 countries. If your app is 10MB or less, you can download it over the cellphone connection, otherwise, Wi-Fi or the iTunes program on your computer.