Apple is now selling the iPhone 4S by reservation-only in the US and Canada, meaning that you’ll need to reserve a unit by 9 PM for pickup the following day. This indicates that iPhone 4S stock is running low, and Apple wants to ensure that customers are able to walk out of the store with an iPhone 4S in-hand.
The “How to Buy” page on Apple’s website has been updated with information regarding this change in policy. The two options are buying online (with a 1-2 week shipping estimate), or reserving for pickup at a local Apple Store.