Apple confirms iTunes account needed to set up iPhone
Apple just sent around an email to those expressing interest in the iPhone. The last paragraph provides a pretty good clue that the rumors of iPhone activation via iTunes is true:
iTunes Account
To set up your iPhone, you'll need an account with Apple's iTunes Store. If you already have an iTunes account, make sure you know your account name and password. If you don't have an account, you should set one up now to save time later. To set up an account, launch iTunes, select the iTunes Store, and click the Sign In button in the upper right corner of iTunes. Sign in and you're ready to go.