The stamp system has recently been phased out. People were found to be stealing stamps in mass quantity and selling them on Ebay. Until August of 2005 the stamps will still be redeemable but they are no longer being given out.
This has sadly created great angst for employees of Subway who must continually say, "I am sorry Miss/Sir. We are no longer using the stamp system. No we do not know what they will do to replace it. No we do not have any cards. I am sorry, but postal stamps don't work."