Stop with the unreferenced wikipedia entry. First you don't say it's wikipedia and second, it's wikipedia.
Until March, Apple never admitted to using Corning glass at all and given that original relationship Corning is happy to oblige Apple by not citing Apple as a customer. according to Pogue's source Apple is the number one consumer of Gorilla glass in 2010. Finally Apple confirmed this in their US Jobs report.
U.S. Jobs Supported by Apple
A study by Analysis Group found that Apple has directly or indirectly created 304,000 U.S. jobs.*These jobs — spread across all 50 states — include thousands of jobs in numerous industries, from the people who create components for our products to the people who build the planes and trucks that carry them to our customers. For example, this figure also includes workers in Texas who manufacture processors for iOS products, Corning employees in Kentucky and New York who create the majority of the glass for iPhone, and FedEx and UPS employees. Together with the 210,000 iOS jobs generated by the app economy, these 304,000 jobs make a total of 514,000 U.S. jobs created or supported by Apple
So clearly the 4S is sporting Gorilla Glass or possibly a special formulation of GG just for Apple. It's not some Chinese knock off that trolls claim or even the Dragontail from Asahi rumored to be used in the iPad 2.