Since there are dozens of similar books about Harry Potter already in print, JKR's stance against the Lexicon is pointless. Nor does she have a leg to stand on, since "fair use" (i.e. a secondary work analyzing a copyrighted work) is a legal and appropriate protection in this case.

Furthermore, JKR has publicly stated that she won't be publishing her encyclopedia for as long as ten years from now, so why is she worrying. Besides, her claim that the Lexicon would eliminate or reduce her future sales is also ridiculous, because any further books she'd publish about Harry Potter would have huge sales, regardless of how many books others may write.

Frankly, I think this has made her look rather small and grasping, although I think that Warner Brothers is behind all the fuss.