Not all happenings in the world can fit between the covers of the New York Times. Herman and Chomsky outline five filters, interrelated to some extent, through which these events must pass in order to become newsworthy.
Media is a business
Huge transnational businesses own much of the media - a fact probably more true now than in 1988 when the book was written with Disney, Westinghouse, and Microsoft bullying in on the news markets. The corporate interests of these companies need not, and probably do not, coincide with the public's interests, and, consequently, some news and some interpretations of news stories critical of business interests will probably not make it to press.
The product is advertising
Since advertising is crucial to keeping subscription costs low, media will shape their news away from serious investigative documentaries to more entertaining revues in order to keep viewer or reader interest and will cater to the audience to which the advertising is directed; Before advertising became central to keeping a paper competitive, working class papers, for example, were much more prevalent, leading to a much broader range of interpretations of events (and thus more room for a reader to make up his own mind) than can be found by perusing the pages of the Wall Street Journal and the Boston Globe.
It reports on what others say, not reality
Media depend crucially on sources and these sources will inescapably have their own agendas. Reliability of information should be important (although it may not be as shown by the tabloidization of the mass media in Monica Lewinsky affair), but the press also needs a steady stream of events to make into news. This leads to a reliance on the public relations bureaucracies of government and corporate agencies for whom some measure of accepted credibility exists and who will also probably have a statement about major happenings. However, by relying substantially on the statements these parties, the media becomes less an investigative body and more a megaphone for propaganda; independent confirmation of facts as well as interpretation eludes it.
Stories must either create successful drama, or downplay all drama
There are costs to producing an incendiary news item -- one which attacks powerful interests whether they be advertisers, government agencies, corporate bodies, or public interest groups. According to the previous three filters, the media relies on these interests for its survival and cannot afford their sustained censure. While none of these filters guarantee that a news item attacking one of these interested parties will not appear, the story is likely to be spun in a way to minimize fallout or flak which may compromise its integrity.
It does not question our implicit assumptions about what is right
Since they wrote at the end of the Reagan years, Herman and Chomsky's final filter is anti-communism, but it may be any prevailing ideology. The assumptions behind ideologies, almost by definition, are rarely challenged; ideologies organize the world, constructing frames into which news events can be placed for easy interpretation: Communism is evil; the domino effect is an actual phenomenon; America is right. This past February there was no hint in the domestic press that there could be any response to Iraq's intransigence other than bombing, making the contrary opinions of the vast majority of the world unintelligible. In domestic affairs, article after article praises various organizations on increasing the diversity of their membership -- diversity being always ethnic and racial diversity without ever asking why racial and ethnic diversity is necessarily relevant in the first place (as opposed to diversity of political opinion, for example).
(This was Lard_Baron's summary of the documentary "Manufacturing Consent," but it's a faster and more concise read than watching the film can provide. I made minor edits for readability and reposted it here.)
All good points; there is one addition from the Vijay Prozak canon: Crowdism:
Think for a moment: what sort of problem is it that one cannot identify and root out? The simple answer: one you cannot tell to another person, and therefore, even if you know it, no one else can work on the problem - and in modern society, every problem is too big for one man. Imagine working with another police inspector on this case. You can tell the guy everything except that which might potentially hurt his feelings. So the investigation goes on, and despite your partner being slower than you are, he puts his heart into it. At the end you have no answers, because both of you don't know the answer, even though it's in your knowledge.
The dirty little secret of the West's collapse is that it has come from within. The extent of our modern disease is revealed by the fact that when we think this, we immediately try to blame either everyone, or no one. We are afraid to blame a process and implicate certain people as its methods. And why not? We're not passing moral judgment, claiming them to be the spawn of Satan, as our leaders do to enemies during wartime. All we are saying is that they, by what they do, have caused a massive problem. The real social taboo broken here is the unstated obvious: in order to fix the problem, we have to limit their sainted "freedom." Nevermind that few people actually need freedom. What they want are normal, comfortable lives, without other people intruding in upon them and telling them what to think. That's not freedom; it's common sense and common decency. People like to conceive of "freedom," however, as a limitless absolute. "I can do anything I want," they say, forgetting that most of what they actually want falls within the narrow sphere of what benefits them in a practical sense.
[I]magine that something needs to be done for the good an entire community. Healthy people are willing to make sacrifices for this. But some would prefer to rigidly negate that proposal because it interferes with their personal fortunes or convenience. By doing this, they are dooming the community in the long run, even if it means they get to keep whatever it was they desired in the short term. These people need some kind of protection that, no matter what the overall goal is, justifies their selfishness. Even better, it should eliminate the concept of overall goal, and focus only on the individual. To do that, a morality was created which banned actions and not goals, effectively hobbling any goal-setting because any real change will always infringe upon someone's little world. Morality is the assertion of personal reality as a higher value that physical, this-is-the-real-world-pay-attention reality.
Crowdism by Vijay Prozak
Media is not the cause; it is the (pardon the static pun) medium through which the virus of Crowdism moves. We are right because we celebrate the individual; we must draw attention to ourselves or fit in to gain social status; those who oppose us are wrong because they are not moral.
When you learn to recognize the virus of Crowdism, which is individuals arguing for absolute autonomy for others so they can have it for themselves while being oblivious to the consequences of others having it, namely a pervasive social decay through fragmentation of consensus about values and goals, you can see that media, like other products, is a manifestation of our own desire to recede within ourselves and not face the conflict and reward structure that life offers.