They just can't try to directly influence the 25,000 or so Nielsen families whose viewing habits determine those ratings.

Oprah Winfrey was reminded of that rule after she took to Twitter and invited viewers -- especially any with "a Neilsen box" -- to tune into her struggling OWN network. She sent the tweet Sunday and soon deleted it, she said, at Nielsen's request. In a statement she apologized and said she "intended no harm."

Why the quick retreat? Because you can give away cars to everyone in your studio audience to get people to watch your show. You just can't ask people with Nielsen boxes to watch it.

Who made this rule? The good people at Nielsen, of course, who want to ensure that their ratings are never clouded by something as unseemly as -- shudder -- a direct appeal to viewers.

"In accordance with our policies and procedures, Nielsen is reviewing this incident with our clients and we may withhold, breakout and/or make a note in the ratings," Nielsen said in a statement. "We take any violation of our policy seriously and will work with clients to resolve the situation."

The television industry supports the rule as well. A Media Rating Council resolution opposes attempts to "exhort the public to cooperate with station audience measurement services... because of its possible biasing effect." In other words, trying to get people to watch may result in them actually watching.

There's a reasonable basis for the rule: You don't want every Nielsen family to be bribed with new cars in the driveway, for example. That might lead to a terrifying world in which dumb, lowest-common denominator shows thrive even as intelligent, challenging ones are cancelled.

It's unlikely that Winfrey's tweets caused any huge spike in OWN's ratings that Nielsen will have to explain, break out, or even refuse to record. Winfrey took to Twitter at the worst possible time, during a Grammys ceremony that turned out to be the second-most watched ever, thanks in part to its many Whitney Houston tributes. Winfrey may as well have cadged for viewers during the Super Bowl.

Nielsen's review drew stories from The New York Times, The Washington Post, and many other news outlets. Some accused Winfrey of "begging" for viewers by asking them to watch her shows, as did many on Twitter.

OWN has earned lower ratings than Discovery Health, the network it replaced last year at a cost of hundreds of millions of dollars, and the Twitter incident struck a chord because it seemed emblematic of her ratings troubles.

It suggested that the Queen of Talk would stop at nothing to get Nielsen families to watch -- even asking them to watch.

(Editing by Chris Michaud)

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