DVRs Contributing to Falling TV Ratings?

In the article, Where have all the viewers gone? from CNN.com, the author cites Digital Video Recorders as a possible reason why ratings have dipped dramatically this TV season. Because Neilsen only counts recorded shows watched within 24 hours of its live airing, there is a perception by advertisers that less people are watching, when in fact people aren't watching less TV, they are just watching in different ways.