Overread
Searching for a flower
Well, GRRM learned from AFFC. He gave plenty of updates... but he was overly optimistic and he got negative reaction for it. So now he's keeping mum so as not to anger his readers... and he's getting negative reactions. Poor guy cannot win.
This is something a lot of new-start companies learn. I saw Spartan Games (miniature model makers) get into that trap. They posted lots of early development concepts and designs as they worked on them; but because it was so early in the design phase when things came up which caused delays or which caused resources to be pulled off that project for a time it resulted in a loss of trust in the developer and the product. People just saw continued delays or no new information and assumed the worst.
Thus sometimes its best to say nothing at all.
Most people don't "get" creation of products/books/films/etc.... They don't appreciate the amount of time that goes into them nor understand all the common and normal pitfalls (we like to think the creators are so skilled as to be beyond mistakes!). In short one has only two real options - exceptionally regular updates which keep people up-to-date on a weekly basis or at least bi-monthly. Or you say nothing until the product is done and pretty much already in the phase of production where you're making it or so close that you nearly are.
The regular updates is possible with some products; but with a book its hard because its not just write it start to finish - chapters get moved, added to, removed. You could write 5 in one month then in the next delete two and write no more fresh ones. It also takes time to make updates - that's more time - more distraction - more discussion - more elements away from working on the project.
GRRM takes his time - we love his work and thus should be patient with waiting for it to be ready. Really the only "anger" is frustration and a degree of fear that he will take his creation to the grave without telling us the ending. People are afraid (insert Yoda quotation) we just have to accept that what is is what is and wait. (and maybe read something else)