And who better to comment on it than Jeff Jarvis, former TV critic for TV Guide, People and creator of Entertainment Weekly:

TV just exploded

: The inevitable just happened: The broadcast networks earned less in upfront (preseason) ad buying this year than last year. That’s a big deal. It’s not a cycle. It’s an explosion. Mark this date as the day TV exploded and the mass market went pfffft with it.

It had to happen. Year after year, network audiences declined, yet ad rates and buying went up: Marketers were paying more for less (and I thought only cable customers did that). The delta between those two lines on a chart is a measure of advertisers’ inability to change or worse. But now that has changed.

It’s all downhill from here. Oh, this doesn’t mean that broadcast is dead. But it will not grow again. It will shrink. Ditto other big, old media outlets. And with that, the media industry will change as it is forced to find new ways to produce lower-cost programming and as advertisers are forced to abandon easy mass-market buying in favor of putting together ad hoc, targeted, and more efficient networks in more measurable media, including media created by people outside media companies (aka you). The dollars will flee to online and its many media at a higher, faster rate than audience declines on the networks as advertisers finally begin to value online appropriately (though online is a scarcity killer with unlimited content and traffic and that will depress rates).

Check out the rest of his post for more poignant thoughts.