Designed I believe for readers who think Tolkien (there are still people who can't spell the name: 'i' before the 'e' for goodness sake!) and J.K. Rowling are all there is (I can only bring myself to mention the two in the same sentence if the context is popularity and sales, otherwise there is no reason for J.K. Rowling to exist in the same sentence as Tolkien!).
Adam Whitehead's caveats seem pretty much spot on for me. Quite why Terry Goodkind is on the list (even taking into account the explanations in the recommendation list itself) when Martin is not is baffling. Probably because the TV outing of Goodkind's series is already well on the way, while Martin's vastly superior work on every level (not least of all the writing) is still being cast.
The omission of David Gemmell ought to be noted, too! In fact what needs to be noted is that despite mentions otherwise the recommendations are totally biased towards North American authors!
I agree with Adam W's points too Nick.
And also your points that it is 'biased' towards North American authors - but then it's understandable - it IS an article in the New Yorker! Also, don't forget that some of the UK Fantasy authors have only become readily available in recent years...
BTW when viewing the page, Adam's comment - the first one on display - was written over the top of the page footer making it difficult to read - was that just my screen?