A year ago, during the May "sweeps" month, there were six million more viewers than this year, according to the New York Times on Monday. While some fled after the writers strike, the real loss has been due to viewers using DVRs and other devices to watch TV on their own terms.

Many of those six million have also discovered Internet streaming video like Hulu and other video on demand (VOD) sources.

The question is, given that appointment television appears to be on the wane and a multitude of video sources have fragmented the audience, what the networks should do next.

Mr. David Wolf, a senior executive with the consulting firm Accenture, thinks that the "Must See TV" nightly lineup of shows is dying. With fewer viewers to account for, even with controversial delayed accounting for TiVo users, the networks can’t depend on an audience glued to the TV for the evening. That will hurt all but the blockbuster shows.

Apple’s iTunes

DVR ownership, now in about a quarter of American homes, is up from 15 percent in May 2007 and has been responsible for a 60 percent rise in recorded viewing this season. With the favorite shows still pitted against each other by the competing networks and often lack of weekly continuity, a DVR is an emerging necessity.

While networks will eventually work out the metrics with Nielsen and financing from advertisers, some of the less popular shows could disappear faster than ever before. That’s likely to bring even bigger changes to TV schedules as viewers have found new ways to watch video on their own terms. It could also introduce an era in which most viewers only pay only for those shows they want to watch, sans commercials -- something that the Apple TV has been promoting since day one.