Viewership was down in the third and fourth quartersIt might be time for cable to start worrying about online streaming. The Wall Street Journal reported that a drop in TV ratings and viewership can be chalked up to subscription-based streaming services, including Netflix, Hulu and Amazon.People familiar with the Cabletelevision Advertising Bureau told the newspaper that as much as 40% of TV-rating declines in the third and fourth quarters were attributable to streaming services. The news comes as TV viewing has declined by an estimated 10% from a year previously in the third quarter, and by 9% for the...