On the night of July 20, while TV crews in many countries were training their lenses on preteens dressed in black capes camping outside bookstores, another group was fidgeting at their keyboards, waiting to rush into the labyrinth of Wikipedia. At 11 p.m. PDT, an hour before Harry Potter and the Deathly Hallows was to be released, the discussion of the book on the “comments” tab of a Wikipedia entry was getting tense.