TVWeek.com has a column on the implications of Digital Video Recording (DVR) made available by the likes of Tivo.  The industry is worried about the apparent drop in revenue generated by advertising, because we're no longer required to view commercials.

"The rollout of DVR-type technology, hastened by its integration in cable set-top boxes as a weapon in cable's battle with satellite for subscribers, will reach critical mass with 11 percent penetration of U.S. television households by 2005 and 15 percent by 2006, Mr. Marsh said. By that time sponsorships and product placement, or even long-awaited deregulation, will offset the rapid loss of spot television advertising revenues.

...But the scariest part about all of this is the lack of response from broadcasters, which do not share Wall Street's emerging sense of urgency about how DVR-type technology is being adapted more quickly and undercutting their ad-supported economics more quickly than previously expected."