Just about everyone that I know would prefer cash over credit. Apple is the complete opposite when it comes to the iPhone. They will no longer accept cash for iPhones. They have also set a limit of 2 per customer from the previous 5. And to top it off you cannot use your $100 gift card that they gave you for buying your iPhone early or use any Apple gift card on that note. In order to get an iPhone from apple you must provide your ID and a credit card.
Due to the fact that recent news has reported that 250,000 iPhones out of 1.3 million sold since launch have been unlocked, Apple is trying to track sales and make sure you activate your Phone with AT&T and are not reselling unlocked iPhones in the masses.