User blog comment:Sarah Manley/Sneak Peek at the New Look - Community Activity/@comment-872086-20100826002425/@comment-961279-20100826063409

In English, you read left-to-right, so having the menu on the left side and sub-menu items expanding out to the right seems like a natural progression. Haven't really used any systems that have right-hand menus that expand out to the left, though, so I don't know if it's a concern or not.