Now, in fairness to the fans, GRRM is partially to blame for the whinging since HE was the one who announced a schedule which he hasn't kept. If you make promises and don't keep them, people WILL whine.
However, the greater point does hold. There are a large number of fans out there (though, one hopes, vastly smaller than the overall group of fans of a given work -- i.e., maybe a few percent of the fans are in this category) who often sound like they hold to the belief that the author exists as a generator of THEIR entertainment (as Scalzi puts it, the authors are "black boxes" of entertainment), and however fast that generator is, he or she isn't fast enough unless there's a new book to hand immediately after the reader's finished the last one.
Of course, the fact is that the author doesn't owe the fans a damn thing except, if the author chooses to pop his head up in public, basic politeness -- which can be exceeded by a "fan" who seems to believe in some form of entitlement.
Some authors do write, in part, specifically for the fans -- not necessarily "to fan specs" but they're writing because they are trying to please some audience, or because they sincerely don't feel that a story is complete if it is not being read. Others do not.
In my case, I'm very happy that people read my books, and happy to discuss them, and so on. But I'm not writing for the readers. I'm writing for me. Fortunately, I can be happy writing a fairly wide variety of things, so if the fans, or an editor, or an agent or co-author, says "hey, instead of something like THAT could you do something like THIS?", often I can find something fun to write that fits the bill. But I can't, and won't, write "for someone else", and if I *did* encounter "entitlement" fans (which so far I fortunately have not personally, though I've seen them for other authors) they'd be likely to make me reactionary and unwilling to write what they wanted. :)