An interesting article by Kent Anderson at The Scholarly Kitchen argues that DVR's allow viewers to pay more attention to their tv-watching - including the ads.
The main point: DVR's give people control over their viewing, so they're more active about what they watch. Passive viewing generally means paying less attention to what's on the screen.
To escape ads before, people would use the time to use the bathroom, make a sandwich, make a phone call, or check email (more recently). In fact, there was once an urban legend about plumbing problems being cause during commercial breaks during the Super Bowl. Running at normal speed, commercials allowed for 2-3 minutes of activity away from the television. Sped up using a DVR, people don’t leave the room.
Viewers have to watch the ads to use a DVR effectively. You have to know when the ads stop and the show resumes, which means watching the ads as they go by. Even at a high speed, the ads register. And people do watch carefully. As Hammock puts it so nicely, “Often, the person with the control is being judged by a second party for their finesse in stopping the fast-forwarding at the precise time it needs to stop, so, therefore a second party is also engaged in looking at the sped up commercials.”
Anderson is certainly right that few people were really watching all those ads anyway. Most of us are multitasking like mad when the tv's on. It's a rare program that has my undivided attention.
As an aside, I don't have a DVR, but I have found that I pay far more attention to a Netflix program streaming to my computer than I do to a DVD playing on the television. This seems to have more to do with the size of the screen than to any other factor. To watch on the computer, I pretty much have to keep the laptop on the lap, and I can't really surf the net or browse a book at the same time. I do like being able to carry it into the bathroom with me, though.