Virtual worlds and big tobacco hold one strategy in common: hook 'em young. It's estimated some 20 million kids will congregate in virtual playgrounds by 2011. To capitalize on their addiction, a growing percentage of virtual architects are focusing on kiddie fare modeled after Webkinz and Club Penguin. Disney, Warner Bros., Viacom's Nickelodeon, as well as Lego, Mattel, and Hasbro are milking cartoon and toy franchises for the stuff of kids' virtual dreams. Disney's launching Pixie Hollow, a fairy-themed world, in time for the release of Tinker Bell this fall. Disney, we have the perfect beta tester for you.