Now, according to internal documents obtained by SprintFeed, Apple has extended iPhone 4S consumers the opportunity to purchase AppleCare+ until December 15, 2011. Apple has also changed its policy and is now allowing all customers 30 days from date of purchase to come back and purchase coverage on the phone.
The main difference between AppleCare and the new AppleCare+ is that the new protection plan covers up to two instances of accidental damage (for a $50 service fee) per coverage period, whereas the old plan did not cover accidental damage at all. Because they are now covering accidental damage, a customer that wants to add AppleCare+ after the phone has left the store must call Apple directly or make an appointment at their local Genius Bar. Apple is requiring a receipt and a phone inspection to prevent people from attempting to purchase coverage after an incident occurs.
source: SprintFeed & Apple via Engadget