"There's something truly creepy about the notion of marketers manipulating what ordinary people say to one another," writes Jeff Gelles. "As a parent, I'm especially concerned when the targets are teenagers like my daughters - which is why I decided to take a look inside Tremor [3]," a Procter & Gamble [4] Web site that has enlisted a quarter-million teenagers as "word-of-mouth [5]" marketers. Tremor uses coupons, discounts, free downloads and product samples combined with "the usual online smarminess" to hook kids into spreading the word about their clients' products.