The older I get, the less interested I become in having a detailed setting that all makes sense. Somebody on the rpg site linked to this io9 article, in which a painfully hip and clever journo sets out "The 7 Deadly Sins of Worldbuilding"; it's the sort of thing I probably would have appreciated 10 years ago, but which I now view as dangerously wrong-headed. Setting aside M. John Harrison's critique (which is that what we know about our world fills umpteen libraries and not even that is enough, so why on earth would you expect a fantasy world to be that detailed?), no fantasy author who you would care to label as being "great" has ever cared about any of those things. Especially not Tolkien, who for some reason is always seen as obsessing over detailed setting creation but who clearly didn't care a jot about economics, infrastructure, non-monolithic socio-political groups, or portraying members of different ethnicities in three-dimensional ways (or having three-dimensional characters in general, really). You could say exactly the same thing about Peake, Wolfe, Vance, Howard, Zelazny, Moorcock, Lewis, Harrison... Even modern authors who are renowned for being interesting "worldbuilders" - Mieville and Martin spring to mind - show no real evidence of considering the creation of a world that makes sense to be one of their key tasks. (I remember reading an interview with GRRM in which he said something along the lines that the Dothraki language has 7 words because that's all it has needed so far, and when he needs an 8th word he'll create it; this seems to neatly sum up his philosophy towards worldbuilding.)
This is because fantasy in general has always been about theme. As long as things are thematically coherent, readers tend not to care about much else: it's never bothered them exactly why it is that The Shire is so prosperous and why we never see female orcs, or where Gormenghast gets all of its luxury goods from. They're interested in the story, and the themes which underlie it, and as long as things aren't egregiously ridiculous they couldn't care less about these "7 Deadly Sins of Worldbuilding". (Indeed, you might say that the moment a reader starts nitpicking about stuff like that is the moment you've lost him as a reader: the reason he's nitpicking is because he's bored by the story.)
I tend to think that the growth in fan-dom amongst nerds in the internet era has contributed to this strange notion that everything has to be perfectly thought-through. Unlike in the 1930s and 40s, when Tolkien was writing The Lord of the Rings, there are now baying throngs of fantasy and SF fans who define themselves by their geekdom and who veritably froth at the mouth at the prospect of debating the minutiae of their favoured franchises with people who are Wrong On The Internet. The game has changed, and not for the better; ultimately I think it is a childish expectation that everything has to fit together, and a childish expectation that everything can be explained.
Of course, I'm not a fan of that other disease of nerd-dom, which takes the view that theme doesn't matter and literally everything that you like should be mixed together, on the principle that I like ice cream and I like spaghetti bolongnese so why on earth wouldn't you want to mix them together? It seems to me that all that's required is thematic coherence and if you have that taken care of, you've won.