This paper explores the emerging relationship between commercial priorities and technological design within children's virtual worlds, through a comparative case study analysis of the promotional contents and marketing features found within six commercial, game-themed virtual worlds targeted specifically to children under the age of 13: Disney's Club Penguin and Toontown, Mattel's BarbieGirls, Cookie Jar's Magi-Nation, Nickelodeon's Nicktropolis, and Corus Entertainment's GalaXseeds. Focusing on key trends identified across all six cases, the paper argues that these games are designed to mobilize virtual economies for real money transaction and self-promotion, utilizing game mechanics, virtual items, and other features for various forms of branding and third-party advertising strategies. A critical analysis of these trends and other relevant findings is provided, through a consideration of how such processes work to mobilize players' affective labor, while concurrently limiting potentially important opportunities for participation, communication, access, and cultural rights, such as freedom of speech.