If you want a long time insider's view into the TV industry definitely read @MaskedScheduler's blog. He wrote a post on the end of the 2009-10 season, and the thing that most caught my eye was (emphasis mine):
There's far less talk about the death of network television but that doesn't mean there aren't challenges to the business. Although most people still watch television the "old fashioned" way the simple fact that there are so many alternatives now (IPod HULU etc.) coupled with the lack of urgency due to recording and time shifting, threatens the communal experience of watching a television show. We just better figure out how to monetize all these platforms or we're screwed.
I'm not so sure that increased choice (cable, videogames, Internet, etc) hasn't played the bigger role in threatening the communal experience than iPod, Hulu, and DVRs, but regardless, the lack of urgency is ultimately a big problem, and not just for the broadcast networks but for the existing advertising-supported business model.
I've been watching the first four seasons of Bones on Netflix. While there's no doubt 20th Century (studio) sees some money for putting its shows on Netflix, whatever it is, it's a pittance compared to TV advertising, even on a per person basis.
Nielsen will begin testing later this year with plans to roll-out early next year a metric for measuring delayed viewing online and on demand. In addition to the DVR tracking for commercial viewing within 3 days, Nielsen will count online and on demand viewing within three days provided it carries the same national commercials that ran on TV.
The semi-good news for the TV networks is that at least for now the biggest percentage of delayed viewing that happens still happens in the first few days. In fact, most viewing of shows still happens live, and on a TV.