TiVo's cool - you can fast forward, and once you see what you want to watch, you press play. It rewinds a bit to account for reaction time, so you press play and see maybe 5 seconds of the last commercial in the break.
If people who bought commercial time were smart, they'd pay more for the first and last slot to advertise better to the TiVo fastforwarding people (and those doing stuff during breaks). I am guessing they already do. But if they were really smart, they'd have the last commercial before a show have a funny punchline. I've rewound TiVo at least twice to see a whole commercial that had a fun ending.
TiVo is actually really cool. I don't watch live TV anymore. I don't discover new shows, but I enjoy the time I'm watching TV more because it's on my schedule and it's the shows I want to watch, not whatever happens to be on..