I was told to watch the television series, "Lost" but that maybe I should wait until the DVD for the season comes out. That way, I can avoid commercials and not have to wait a week for the next episode.
A friend followed my advice and watched an episode of Battlestar Galactica. because he hadn't seen the mini-series that preceded the current series on the Sci-Fi channel, he was sort of lost (oops, no pun intended).
Given the availability of television series on DVD, people don't feel they are losing out if they miss an episode or half a season for a television series. They'll be able to rent or buy the DVDs.
Surely this will bite into a show's ratings. Television series DVDs have been said to be the hottest selling segment of DVDs currently.