Um, it only takes a moment's reflection to realize that there have been several dozen unauthorized Harry Potter books being sold for years now and Rowling hasn't gone after any of them.

The difference in this case is that the Lexicon was to be composed almost entirely of unattributed quotes directly from her books, as opposed to new material written by the 'author'. It was basically an encyclopedia, but rather than describe people, objects, etc. in his own words, Vander Ark lifted relevant passages straight out of the books, with at most a note referencing the chapter number but often not even that much. According to court testimony, the book was over 90% Rowling's words, and not Vander Ark's. This goes far beyond anything resembling Fair Use.

If she were trying to prevent any use of her world at all and fighting any sort of fan works, I'd be in complete agreement with the sentiments in this thread. But that simply isn't the case here.

The knee-jerk reactions in these comments based on knowing nothing more than the couple of paragraphs quoted above are sad and a little scary.