I think one of the reasons people zap through ads -- and a widely overlooked one- is THAT THERE'S JUST TOO MANY OF THEM. The average ad pod is now close to 4 minutes (or it sure seems that way) and if I'm in the middle of watching a show, I just don't want to sit through that long an interruption.
Now if there was a 60 second commercial break, I wouldn't bother reaching for the remote. Time/benefit analysis says it wouldn't be worth the effort.
Wonder why no one's thought of that before.