There's the rub - TV is inherently a passive activity. How do you get people to actively report their viewing habits when all they want to do is sit on the couch and vegetate?
Most normal Neilsen ratings require no regular active participation. In every broadcast they embed signals in the audio and video that the neisen box can pick up and it phones home. The only time they use diaries is as a supplement during the 4 sweeps weeks each year.