More than two months have passed since America Online and Time Warner announced plans to merge. Big news at the time, the formation of the world's largest media firm is already old hat. And so it goes: Like the rest of us, journalists quickly get used to the latest consolidation of media power.

One of the country's most perceptive media critics, Herbert Schiller, died a few weeks after the unveiling of AOL Time Warner. A professor of communication, Schiller had been warning against such corporate trends for decades. He urged people to consider the dire consequences when giant companies dominate and wield the latest media technologies.

"It is not necessary to construct a theory of intentional cultural control," Schiller observed in 1989. "In truth, the strength of the control process rests in its apparent absence. The desired systemic result is achieved ordinarily by a loose though effective institutional process."

Schiller's book Culture, Inc. -- subtitled "The Corporate Takeover of Public Expression" -- went on to cite "the education of journalists and other media professionals, built-in penalties and rewards for doing what is expected, norms presented as objective rules, and the occasional but telling direct intrusion from above. The main lever is the internalization of values."

Self-censorship has long been one of journalism's most ineffable hazards. The current wave of mergers rocking the media industry is likely to heighten the dangers.

To an unprecedented extent, large numbers of American reporters and editors now work for just a few huge corporate employers -- a situation that hardly encourages unconstrained scrutiny of media conglomerates as they assume unparalleled importance in public life. Like the Viacom-CBS merger announced last fall, the joining of AOL and Time Warner puts a lot more journalists in an awkward position: on the payrolls of media outlets that are very newsworthy as major economic and social forces.

Many of us grew up with tales of journalistic courage dating back to Colonial days. John Peter Zenger's ability to challenge the British Crown with unyielding articles drew strength from the fact that he was a printer and publisher. Writing in The New York Weekly, a periodical burned several times by the public hangman, Zenger declared in November 1733: "The loss of liberty in general would soon follow the suppression of the liberty of the press; for it is an essential branch of liberty, so perhaps it is the best preservative of the whole."

In contrast to state censorship, which is usually easy to recognize, self-censorship by journalists tends to be obscured. It is particularly murky and insidious in the emerging media environment, with routine pressures to defer to employers that have massive industry clout and global reach. We might wonder how Zenger would fare in most of today's media workplaces -- especially if he chose to denounce as excessive the power of the conglomerate providing his paycheck.

Americans are apt to quickly spot and automatically distrust government efforts to impose prior restraint. But what about the implicit constraints imposed by the hierarchies of enormous media corporations – and internalized by employees before overt conflicts develop?

"If liberty means anything at all," George Orwell wrote, "it means the right to tell people what they do not want to hear." As immense communications firms increasingly dominate our society, how practical will it be for journalists to tell their bosses -- and the public -- what media tycoons do not want to hear about the concentration of power in few corporate hands?

What Schiller urged many years ago is now more crucial than ever: We need a vibrant political movement that "would aim at reducing private monopoly power over news, TV programs, films, music, data processing, publishing, and advertising. It would encourage the availability, as much as possible, of information as a social and inexpensive good, not, as increasingly the situation, as a salable commodity."

While mega-media machinery spins into even higher gears, Herb Schiller's vision is compelling. He saw that the status quo, shaped and constrained by the power of money, routinely limits our sense of cooperative ingenuity. But very different options remain, including "vastly expanded public support and encouragement of noncommercial expression and creativity. Publicly financed newspapers, magazines, television, radio, theater, and film would become a legitimate part of the national social landscape.... The important consideration is to allow for imaginative alternatives. Currently, the fashion is to deny that possibility."

Norman Solomon is a syndicated columnist. His latest book is The Habits of Highly Deceptive Media.