There's nothing "grey" about the anatomy of ABC's first week in the fall ratings books. Disney's (NYSE:DIS) ABC was the most watched network last week, cashing in on the success of shows such as Grey's Anatomy, Dancing With the Stars, and Desperate Housewives.

In fact, ABC claimed five of the top six slots last week, according to Nielsen Media Research, while CBS (NYSE:CBS) had the most-watched show with the season premiere of CSI.

This is a tremendous turnaround for the network. It used to dominate the fall ratings book. Between Monday Night Football and as many as four nights of Who Wants to Be a Millionaire, two franchises were enough to give Disney a healthy start to the primetime season. However, weakness elsewhere in the network's programming was exposed when fans got burned out on the overexposed Millionaire quiz show. Then Disney decided to move its Monday gridiron contests over to ESPN.

But even more impressive than ABC's strong start is the shocker that NBC was the top draw for audiences in the coveted 18- to 49-year-old demographic group. NBC, which is majority-owned by General Electric (NYSE:GE), can thank Heroes and Sunday Night Football for that, as well as a strong showing by the Bionic Woman debut.  

Strong starts don't imply strong finishes, though. News Corp.'s (NYSE:NWS) Fox may seem like a non-factor at the moment. House was its only show to crack the Top 20 last week. Fox will get a considerable push higher when 24 and the seventh season of CKX's (NASDAQ:CKXE) American Idol return come January.

And don't think that watching the ratings is strictly a couch-potato sport. Advertisers flock to popular shows like birds to a power line, so healthy ratings and strong ad revenue go hand in hand.

This season also has some compelling implications as digital distribution through Apple (NASDAQ:AAPL), Amazon.com (NASDAQ:AMZN), and the networks' own namesake sites plays a bigger part of primetime consumption.

In short, it pays to watch what everyone else is watching.

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