Ansel Adams is 23th and Cindy Sherman is 14th? Look at a 1000 Flickr pictures and tell me who is the more influential. Notice this is not about the greatest, which is very subjective, but about influential which is even more subjective. I bet if the magazine was published in New York or Tokyo, it was be a radically different list.
Andre Kertesz should be at the top (HCB said he did nothing that Kertesz didn't do first) and some of the exceptions (especially women photographers) shows me this is to sell a magazine, not to actually provide any meaningful thought.