When I knew less than I do now, I thought that the "audience" would move to the web and bring the money. I thought that we had more time in TV to adapt. But for a year or so now I have seen that the money is moving first. The web is simply the most cost effective place.
Now with the economy in free fall and the anchor of advertising being in the auto sector and financial services - the shift is accelerating. With much less to spend, they have to make the best of what they do and the web is where the smaller amounts of money will go.
There is no time left. If my simple alarm call does not speak to you - then the brilliant Diane Mermigas has a more detailed argument here.