Ratings are down across the board in prime time as well as daytime and it is because of the fractured market. Television in general has taken a hit as well as print media. The only medium that hasn't suffered in quite the same way is radio, although the satellite radio channels didn't do well enough and Sirius has already folded up shop.
The general feeling in the industry is that this trend will continue and is the reason that so many networks and public broadcasters are pouring money and attention into their interactive departments. The writing is on the wall and they are determined to survive by beefing up online access to their product.
(My husband works in the industry and talks about this all the time.)
Another downfall for the ratings is the DVR. I can tell you that I almost never watch tv live. Not that it matters since I don't have one of those ratings things in my house