Tom Sullivan took screen shots of 52 of the top ecommerce sites on his iphone to see what the support was like. Only 6 of the 50 retailers redirect iPhone users to a mobile-optimized website: Amazon, Best Buy, Foot Locker, Target, Victoria’s Secret, and Walmart. (Ralph Lauren should be on this list, since they offer a mobile-optimized website, but the server doesn’t redirect iPhone visitors.) I am pretty sure this ratio will change quickly considering how important the iPhone has become.
(thank you Jon)