Here's a good article on how U.S. viewers used BitTorrent to watch the first episode of Battlestar Galactica months before it aired and what it means for the broadcast television industry.

While you might assume the SciFi Channel saw a significant drop-off in viewership as a result of this piracy, it appears to have had the reverse effect: the series is so good that the few tens of thousands of people who watched downloaded versions told their friends to tune in on January 14th, and see for themselves. From its premiere, Battlestar Galactic_a has been the most popular program ever to air on the SciFi Channel, and its audiences have only grown throughout the first series. Piracy made it possible for “word-of-mouth” to spread about _Battlestar Galactica.