Here's more about the campaign against age-banding on children's books. From an address by Philip Pullman:
I did not intend the book for this age, and not that; for one class of reader, and not others. I wrote it for anyone who wants to read it, and I want as many readers as I can get, and I want to meet them honestly. And the effect of this little printed figure will be to put at risk the relationship between the author and the reader, by introducing a falsehood into it. For a book to claim "This was written for children of 11+", when it simply wasn't, is to tell an untruth.
(Via Julie Bertagna.)