This book was written during the Reagan era, when the USA was still engaged
in the Cold War against the Soviet Union and in countless proxy wars around
the world. Noam Chomsky here focused on the fact that the free media in the
USA were delivering a biased version of the facts (a sort of "propaganda")
even though technically they were free to report what they wanted.
Chomsky is correct, and probably saw confirmation of his theory in the
run-up to the Iraqi invasion of 2003, when very few media dared to criticize
the assumption that Saddan Hussein was worse than other dictators or that
he had weapons of mass destruction (it turned out that others, such as North
Korea, really had them). The cheerleaders of the Bush administration at Fox
News as well as the fascist propaganda bosses such as Rush Limbaugh
routinely accused of "anti-americanism" anyone doubting the official story
(and they never apologized for being dead wrong).
Chomsky lists a number of factors that influence what the media report: 1. they need government approval to be in business (this is more true in countries such as France and Britain, where the government even funds the media, than in the USA); 2. they need to sell advertisements in order to survive financially and advertising comes from the corporations that direct government policies; 3. grass-roots movements driven by special interests may hurt the circulation of a newspaper by generating negative publicity. Then Chomsky goes on to list examples (mainly from Latin America) in which the media were not objective: the enemy of the USA was consistently portrayed as evil and wrong, while the allies of the USA were forgiven for doing and saying much worse things. Atrocities committed by the enemy were routinely emphasized, while atrocities committed by friendly forces were routinely ignored. (In some cases i suspect that it's Chomsky who was biased, as the post-war facts seems to prove that after all some of the atrocities were never committed and that the people were indeed on the side of the pro-USA dictator, e.g. in Guatemala).
Raading this book in 2010 one wonders if the media have improved the quality of their coverage. Obviously the pervasive nature of the Internet media has made it more difficult to lie about distant events and easier to hear the version of the other side. The bias however remains (e.g., public opinion in the USA approves of the sanctions against Iran but does not demand similar sanctions against another illegal nuclear power, Israel). And the bias is probably due more to the people than to the media: the media tell the people what the people want to hear. It is not clear that it is the media that shaped the people's minds. There are preconceptions about various regions in the world that preexist whatever the media tell people.