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A few years ago, over dinner in Manhattan, a CBS network executive started talking about breakfast.

“A lot of people like cornflakes for breakfast,” he said. “Not too many like cornflakes for dinner.”

He was talking about Katie Couric, who wasn’t doing well in the ratings.

It’s an interesting way to look at it. Katie was cornflakes, immensely popular at breakfast time. Not so much at dinner time when people crave more substance.

But who knew five years ago when CBS News decided to pay Ms. Couric $15 million a year to take over the anchor chair that it wouldn’t work out. That she would start in third place and end up in third place – and with even fewer viewers than she had in the beginning.

So Katie Couric, who had the pre-requisites -- name recognition, a great smile, and a history of success -- seemed like a good pick. Except, as William Goldman, the screen writer who wrote "Butch Cassidy and the Sundance Kid," among many other big movies, once famously said of the entertainment industry: when it comes to picking winners, “nobody knows anything.”

So who’s next? The only honest answer at this point is who knows. But whomever CBS picks, it’s going to be an uphill climb. A lot of TV viewing is a function of habit. You pick a network newscast for all sorts of reasons and it usually takes a lot for you to switch. One thing, though, is for sure. Millions of viewers who don’t normally watch the CBS Evening News will tune in during the first week of the new program. They’ll want to see who the new (probably) guy is and what all the fuss is about. They did that when Katie took over. But before you could say “cornflakes” they were gone. The same thing could happen again with Couric’s successor. But the fact is, “nobody knows anything.”

And then there’s the biggest problem of all for the new CBS anchor – and for all the others. Network evening newscasts are an idea whose time has come – and gone. They made sense 30 or 40 years ago, before cable television and the Internet. Back then, if you wanted to see national and world news on TV you had to be in front of your television set at dinner time. If you weren’t there, you didn’t see Walter Cronite or Huntley and Brinkley. It was your loss.

Now, you can get the news at seven in the evening or two in the afternoon or noon or four in the morning. And you can get it on television or on your cell phone or on your computer or on your underpants. It’s everywhere all day long. Cronkite was the most trusted person in America. Does anybody really think Brian Williams or Diane Sawyer is the most trusted person in America today? Or to put it another way: the network evening news isn't that big a deal anymore.

So good luck New CBS News Anchor Person, whomever you are. And while it may be true that when it comes to picking winners “nobody knows anything” this much I am absolutely sure of: You’re going to need all the luck you can get.

Bernie Goldberg is a journalist, author and Fox News analyst. He is the winner of 10 Emmy Awards and has written five books on the media and American culture, including the No. 1 best-seller "Bias." His most recent book, "A Slobbering Love Affair," is about the mainstream media's fascination with Barack Obama. You can 
learn more about Bernie Goldberg by visiting his website at www.bernardgoldberg.com.