Each week Ross Rubin contributes Switched On, a column about technology, multimedia, and digital entertainment. When Sony included a DVD drive on its PlayStation 2, it was clear which technology was helping sell which product. After just avoiding being a victim of a format war itself, DVD was on its way to enticing consumers with many of the same benefits that had turned the compact disc into a huge success -- high-fidelity, portability, durability and the end of rewinding. The PS2 may well have been a success without DVD, but DVD did not need the PS2. For the PlayStation 3, the issue was a lot murkier. While US sales of standalone -- that is to say, excluding PS3 -- players for Blu- ...