Another prominent financial journalist, who does give paid speeches at Wall Street events, also runs the traps. “I don’t want to be speaking at events run by disreputable organizations—that’s a first filter,” he said.

Are readers really monitoring these journalists that closely? Yes. A financial writer at a leading news organization that bans speeches to for-profit firms told me that, in the current environment, readers are intensely suspicious of how journalists are covering Wall Street. “If I write anything that is even remotely positive about Wall Street organizations, they will send me an e-mail saying, ‘You’re in the pocket of these people,’” this journalist says. “If you were actually in the pocket”—defined, he says, by taking money from the firms for speeches—“that would a real problem.”

Given the varying circumstances and different opinions on the matter, what should the rules be in journalism on speaking fees—taken from Wall Street or anyone else? Robert Dowling, a former assistant managing editor for BusinessWeek who at one point supervised ethics policies, recommends public disclosure—of a journalist’s appearances as well as fees. “It seems hypocritical for the press to criticize Newt Gingrich for taking $1.6 million from Freddie Mac but not tell readers where you as a journalist are earning outside income—and how much,” he says.

I’m certainly no purist on this question. After I wrote a book, published in 2009, about America’s role in the world, I actively sought to give speeches on the university market on this theme, and I still, on occasion, as a freelancer, give paid speeches to nonprofits. I recently was awarded a $1,000 Poynter fellowship to deliver a day’s worth of talks to students at Yale on how media cover Russia and on topics in my book. Such talks can be learning experiences for me—just as Michael Lewis suggested—and there doesn’t appear to be any motive for the university other than to stir thought and debate.

Nor is it evident that Wall Street’s money for speaking engagements has kept journalists, including at outlets with accommodating policies, such as the Financial Times, from providing tough coverage of the financial industry.

Still, the acceptance of speaking fees from Wall Street does strike me as a real problem for journalism. It is a dilemma, most of all, for journalists assigned to the financial industry, because the public has a right to expect that this coverage will not be informed by anything other than the journalist’s reporting and analysis. Any financial journalist—whether a “straight” newsperson or opinion writer—who takes money from Wall Street is inviting skepticism and even cynicism, fairly or not, about the work he or she is doing.

A big problem with speaking income is that, whatever the use of the money—the mortgage, the kids’ college fund, better bottles of wine—the journalist is precisely aware of the source. Even in the case of speaking fees donated to charity, a US citizen is eligible for a tax break, and the appreciation and good works of the group on the receiving end of the donation are also, in a way, things of value to the giver.

And such fees surely have an impact on coverage, if not necessarily an obvious or insidious one. A financial journalist who has been paid for speeches by Wall Street firms told me that he would never write a story about any company that has paid him a fee. Great, except that the more speaking he does, the more he will be restricting his range of coverage. Unconscious self-censorship could be a factor, too, as journalists who enjoy Wall Street’s money might come to feel more simpatico toward their benefactors’ perspectives on various issues. It’s a pretty typical human reaction, after all. The New York Times reported recently that doctors who take money from drug makers often are more willing than doctors who don’t to prescribe drugs in “risky” ways. Why should journalists be any more immune to this than physicians are?

For journalists who take money from Wall Street firms but don’t cover financial issues, the conflict is less apparent. Who cares if a celebrity journalist gets paid to serve as marketing bait for a private-equity firm trolling for new investors? My objection is perhaps more aesthetic than ethical: It’s a little cheesy for a journalist to serve such slick, mercenary purposes. As for big-name journalists who help financial firms buff the brand, that work is better left to the likes of Sam Waterston, the celebrity pitchman for TD Ameritrade.

Paul Starobin , a former Moscow bureau chief of Business Week, is the author of After America: Narratives for the Next Global Age.