By Sharon Duke EstroffAmong the cardinal (albeit unfortunate) rules of the schoolyard social jungle is that the more cool, expensive stuff you have, the higher you climb on the food chain. And what kid doesn’t wish to become king or queen of the jungle? Children’s virtual worlds like Barbie Girls understand this fundamental truth about their target audience, so they lay the groundwork for a social … [Read more...] about Undercover Mom in BarbieGirls, Part 4: Peer pressure to pay up