Tim Wu writes for SLATE,
...Over the last few years, the relationship between fan-written Web sites and the copyright owners of the content they draw on, if legally murky, has at least been peaceful. Once it dawned on media companies that fan sites are the kind of marketing that they usually pay hard cash for, they generally left the fans alone. But things turned sour in the fall, when the Harry Potter Lexicon Web site announced plans to publish a book version of its fan-written guide to the Potter world. Author J.K. Rowling and publisher Warner Brothers have sued the Lexicon for copyright infringement, exposing the big unanswered question: Are fan guides actually illegal?
As sympathetic as I am to Rowling and her rights as an author, the answer is no. There is a necessary and healthy line between what the initial author owns and what follow-on, or "secondary," authors get to do, and Rowling is running over that line like the Hogwarts Express. The creators of H.P. Lexicon may not be as creative as Rowling, but they are authors, too, and deserve a little respect from the law.