Should DVR ever be considered in ratings then it may be a problem. I read a few days ago that Leno has a lot of DVR viewers.
I've never seen Leno so I don't know but is there a lot of built in ad placement or owt like that, then DVR could count more than the norm.
I do remember that they have frequent mentions to Ford on the show especially in the Green Car Challenge.
What's more interesting, and damaging to him, is that ABC and CBS have told their actors/actresses that they are to avoid going onto Leno's show or there could be consequences.