Report: iPhone will accept SIM cards from other phones; cannot act as computer modem
Writing for The New York Times, David Pogue reports that the iPhone will accept SIM cards from other AT&T-sold phones after it has been activated through iTunes with the pre-installed SIM card. This will allow the immediate transfer of contacts and other information to the iPhone. SIM cards from phones sold through other wireless carriers will not work in the iPhone.
Other notes from Pogue's Q&A:
The iPhone cannot act as a wireless modem for desktop/laptop systems You can interrupt synchronization in the middle of the process, and it will resume later To do … Read more