Apple has instituted a reservation-only policy for iPhone 4S retail sales. An online note (http://www.apple.com/iphone/how-to-buy/) by the company says:
“iPhone 4S is available in store by reservation only. Reserve yours after 9:00 p.m. tonight for pickup tomorrow. When you come in, you’ll choose a carrier and plan, and we’ll get your iPhone up and running before you leave the store.”