I worked for a company in 2006 that was considering writing phone apps (we already had a bunch of Windows apps). At the time, each phone company wanted to "curate" the apps for their own phone stores. At least one company wanted, for each $10 app, about $11 of revenue. The result: we decided that it would be essentially impossible to ever make money from phone apps.

What the iPhone did was genius: they created demand for the phone, but would only sell through phone companies willing to let Apple control the app market. That made all the difference: all of sudden, a developer could make an app and have it show up to bazillions of people.

[disclaimer: I currently work for Microsoft, but not in the phone team. But I do have apps in the Microsoft app store!]