My children's artwork adorns the walls of my house in several locations. It is regularly replaced with the most recent efforts, since the preschools seem to excel at a multitude of different craft projects. At home, we favor crayons and washable markers, but we keep close control of them. This evening my three-year-old decided to climb up Daddy's chair and get onto my desk. A ball point pen beckoned from a pen holder placed far from a child-accessible edge. The canvas -- two 19-inch LCD screens....