In a good article, Advertising Age examines the current competing philosophies of CBS and NBC*.
Here's a quick summary of their positions:
CBS: Has had relative success with its broadcast network, and particular success with its scripted shows. No advertising supported cable networks (only Showtime). Sees the future in scripted broadcast programming.
NBC: Broadcast network doing poorly, and scripted shows doing particularly poorly. A strong stable of advertising supported cable networks (USA, Bravo, SciFi, Telemundo). Sees the future in a portfolio of offerings, with broadcast scripted programming de-emphasized.
Looking at it that way, their competing views of the future make complete sense.
The article also had advertising numbers that are a bit different from what we've seen before:
By two traditional measures, CBS has edged out its rival. It's no secret that NBC has seen ratings drop in recent years, while CBS broadened in several categories in the just-finished season. Ad revenue has increased or ebbed accordingly. In 2004, the NBC network captured more than $6.96 billion, while CBS took in about $6.12 billion, according to TNS Media. In 2008, the positions have reversed: CBS captured about $6.3 billion, while NBC took in about $5.4 billion.
Although it does fall into the "CBS up the most this season" trap without mentioning they were down the most the previous year, and so their two season performance isn't as special.
Update edits: Added a summary, the photo and modified the post title.