Of course, lots of people won't want to fiddle with pre-paid SIM cards. That's okay: Both Sprint and Verizon will ship their phones with a "roaming SIM" that's tied to your account with those carriers and uses the networks of their international partners. So if you take your Sprint or Verizon iPhone 4S overseas and never pop out that SIM card, it'll work just fine--you'll just pay the higher data and voice rates that come with international roaming.

Just so there's no confusion, here's Mermelstein's verbatim statement:

Sprint's policy is to have the iPhone 4S SIM locked to our network domestically and internationally. At launch, the International SIM will be unlocked. We do expect a SIM lock to be pushed to the devices shortly after launch. We will then allow existing customers in good standing to unlock the SIM for international use if needed in the future.

Customers can sign up for one of our international rate plans and use this phone all over the world. When traveling internationally, there is a setting that must be turned on within the device to connect to GSM. The phone will work with a SIM that is provided within the device out of the box. International voice and data charges are on a pay-as-you-go basis and vary based on the country where the customer is using their phone; a list of rates is available at www.sprint.com/international.

Sprint offers two international voice plans that customers can subscribe to for discounted voice rates: