Each week Ross Rubin contributes Switched On, a column about consumer technology. Ever since the tablet market exploded, we've seen we've seen a wide range of designs find both success and failure. But most of the tablets on the market have something in common: they are primarily designed for adults or at least children old enough to be responsible for a fragile device. Particularly for the popular iPad, we have seen a number of specialized cases design to protect the tablet for use with young ones. But a small cadre of tablets aimed specifically at kids -- including preschoolers -- begs several questions. Are tablets good tools for kids? Is there value in optimizing them for kids? And if so, how should they be optimized?