Here's why free-for-all comments are a bad idea. Kathy Sierra, the writer and developer, has made a complaint to the police, and has pulled out of a speaking engagement, after what she says were death threats against her on a website. Sierra, author of Creating Passionate Users, had been due to lead a seminar this morning at Etech, the O'Reilly tech conference in San Diego. Among those she's accused of complicity in the online abuse: Chris Locke, aka Rageboy, one of the authors of the Cluetrain manifesto, a bible for marketers. Why do these debates between web geeks become so venomous? Because, as Henry Kissinger said about academic infighting, the stakes are so low.