“I turn down 20 paid gigs for every one that I do, and I don’t particularly like to do them,” Lewis said in an e-mail. “Raising of course the question of why do any paid speeches for anyone, the answer to which is: a) it feels insane not to do a few of them; b) it actually helps me, as a writer, to be forced to air views and material in front of a live audience; and c) I often pick up valuable material from the hosts.”

Lewis went on to say, though, that since the financial crisis he has “turned down anything from anyone who took bailout money, but not because I worried they might be paying me to be more polite about them. I didn’t think that businesses being kept alive by public subsidies should be paying speaker fees at all to anyone.”

Fees vary widely. Niall Ferguson’s “booking fee range” is $50,001 and up, according to the All American Speakers website. In 2011, he spoke at a Las Vegas conference sponsored by Skybridge Capital that The Economist called the “Davos for the hedge-fund world.” He didn’t respond to a request for comment.

Fareed Zakaria, host of the weekly CNN show Fareed Zakaria GPS, has a rate of $75,000, as reported in Harper’s. His general topic on the show is geopolitics, but he has covered Occupy Wall Street and the European financial crisis and interviewed Mohamed A. El-Erian, the CEO of the investment firm Pimco. Over the years, he has been retained for speeches by numerous financial firms, including Baker Capital, Catterton Partners, Driehaus Capital Management, ING, Merrill Lynch, Oak Investment Partners, Charles Schwab, and T. Rowe Price, according to the website of the Royce Carlton speakers bureau.

Zakaria didn’t respond to a request for comment, either, but a CNN spokeswoman said: “We have full confidence in Fareed Zakaria’s professionalism and judgment and do not think his outside speaking appearances interfere with his CNN responsibilities on his weekly show or his commentary on CNN.”

The fees might sound like big money—and to most journalists, they are. But to Wall Street, they’re peanuts, a readily justifiable expense. One reason financial firms hire high-profile journalists for speeches is for favorable brand association. Back in November, Bank of America issued a press release touting its engagement of Malcolm Gladwell, a star staff writer for The New Yorker and best-selling author, for a series of speeches “to deliver quality education and actionable advice to small business owners in various markets throughout the country.” The entire point seemed to be to forge a public link between a tarnished brand (the bank), and a winning one (a journalist often described in profiles as the epitome of cool). Criticized as “a shill” for Bank of America by Jason Linkins of The Huffington Post, Gladwell told The Atlantic Wire that, “like any number of other writers these days who do speaking on the side, I’m happy to chat about whatever I’m working on to whomever wants to listen.”

But there are many occasions when the event is private and exclusive. Asked about a talk that Zakaria once gave to Baker Capital, a staffer at the Manhattan-based private-equity firm said only that the event took place at the Boathouse in Central Park and was for investors. A request to senior management for more details went unanswered.

So what’s the point of hiring journalists for such unpublicized events? It’s possible that attendees glean insights that are useful for their investments in the securities markets—as suggested by some of the comments on Gillian Tett’s speeches. But it’s hard to see how professional investors are going to learn much of actionable value from a journalist, even an accomplished one. The exception might be for political insights about, say, government regulation or taxation of an industry. Journalists often do possess such insights—and Wall Street firms employ an army of political-intelligence gatherers in Washington, typically lobbyists and consultants, to be as up-to-date as possible on actions that might affect investment holdings and strategies.

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