(FORTUNE Magazine) – There's nothing new in the notion of business school professors straddling the divide between the ivory tower and the marketplace. They've always taken consulting gigs and seats on corporate boards, and hired themselves out as expert witnesses. B-schools allow it, within limits, for two reasons: because business is a practical discipline, and practitioners really do bring something to the classroom; and because they have no choice. They can't possibly pay their faculty stars enough to match their market value. Take Mohanbir Sawhney, the marketing expert and McCormick Tribune Professor of Electronic Commerce and Technology at Northwestern's Kellogg School. Sawhney has no illusions whatsoever regarding his worth: "If they ever start saying, 'You can't do any of this stuff,' I would say, 'Well, you've got two options: Either you pay me three million bucks a year or I'm resigning today'... I really don't care. [Kellogg] is not where I'm making my living."

The "stuff" that Sawhney's involved with doesn't just straddle the divide; it obliterates it. With seats on five boards of directors and 16 advisory boards, mainly pre-IPO Internet startups, Sawhney has taken the old model of professorial moonlighting and turbocharged it for the new economy. He combines teaching with heavy doses of popular journalism, consulting, networking, deal brokering, headhunting, and intensive entrepreneurial coaching of the sort normally performed by angel investors and venture capitalists. A new vocation wants a new appellation, and Sawhney, who pioneered the concept and seems to have stretched it about as far as it will go, claims naming rights. "I'm an intellectual capitalist," he says.

So is Steven Kaplan at the University of Chicago, although he'd rather not say too much about it. ("Write more about Mohan than me," he requested.) Sawhney and Kaplan serve on several boards together and are among the co-founders of Michigan & Oak, an early-stage startup consulting firm in Chicago. "Together, we've pretty much locked up the Chicago-area deal flow," says Sawhney. Other examples: Yale's Barry Nalebuff, who agreed to help former student R.S. Ophir with a startup called Split the Difference, but only after Ophir dropped out of school; Florian Zettelmeyer of the Haas School at Berkeley, who advises PurpleTie.com, a startup that hopes to consolidate the $24 billion dry-cleaning industry, meanwhile collecting valuable customer data with scannable labels; and Harvard's William Sahlman, who, like Kaplan, prefers a low profile. In response to FORTUNE's request for a complete list of his startup affiliations, Sahlman wrote back, "I do not hand out such lists to anyone but the dean and my wife."

None, however, can compete with Sawhney--not in the scope of his operations, and not in his willingness to conceptualize what he once referred to, jokingly, as "my scam."

"Here's the basic idea," Sawhney explains one afternoon in the back seat of a taxi on the way to Boston's Logan Airport. (He flew in in the morning for a guest appearance at Harvard Business School, and has an eight o'clock lecture back in Evanston in the evening.) "The thing I was talking about today was that in business-to-business e-commerce, we start to see these hubs of market makers emerge that are becoming switchboards between buyers and sellers. That's what I have evolved into: a human hub that mediates between a whole bunch of constituencies. On the one side, it's current students. Then there are alumni and the executive audiences that I teach. I touch somewhere between 500 and 1,000 people a year, face to face in a classroom. Then, also, I write, so I touch a whole bunch of other people who have read my work, who number now in the hundreds of thousands. I also work closely on the other end of the network with venture capital firms and with people who have startup ideas, as well as bigger companies looking for investment opportunities. And also the academic community. I'm at the center of a lot of deal flow, a lot of people flow."

Like angels and VCs, Sawhney demands equity from his client companies. Typically, he commands a 1% or 2% stake in every enterprise he advises, but he gets more from his early-stage clients, who may come to him with nothing more than an idea. For Sawhney, the upside is enormous. "If a company does well and I don't make a million dollars, it's not worth my time." One difference: Unlike his VC counterparts, Sawhney doesn't put up any money, only his time and intellect. Although he says he steers clear of companies owned by current students, once the student graduates, he says, "all bets are off."

Sawhney notwithstanding, the reticence of most ICs is understandable. To the extent that professors are leveraging their access to bright young MBAs for personal gain and falling over one another in a lusty grab for Internet equity, that's unseemly. Harvard recently tightened up its policy to explicitly prohibit faculty involvement in student-run businesses; other B-schools are considering following suit. But as Harvard's Sahlman says, in these times of unmatched entrepreneurial fervor, "there's all manner of potential poison in the air," not all of which can easily be regulated. Professor John Freeman, who oversees Haas' student business incubator, says, "I have a problem if the students believe, rightly or wrongly, that their access to an educational opportunity is contingent on their giving the professor or a staff member a piece of the action."

Most B-schools formally limit professorial moonlighting to one day a week, or 50 days a year. Harvard goes so far as to require its faculty members to submit a signed, detailed summary of all their outside activities. Kellogg is less strict, at least where Sawhney is concerned. By his own estimate, Sawhney spends at least half his time taking care of personal business, and that's fine with his boss. "I guess when it gets too far, we'll know it," says Donald Jacobs, Kellogg's longtime dean. "So far, it isn't too far. So far, it's an extraordinarily productive personality working and creating an environment that's absolutely invigorating for the people here.... I don't think there is a question that he is giving us our due." Jacobs even went so far as to award Sawhney a highly unusual five-year guaranteed contract with professorial rank and an endowed chair despite Sawhney's relatively sparse academic publishing output and lack of tenure.

For all his bravado, Sawhney knows that he needs Kellogg as much as Kellogg needs him. "It gives me a platform," he says. "It gives me an affiliation. And it gives me credibility that goes beyond being a consultant. And the reason that those people in some instances affiliate with me is because I'm part of the institution."

At Logan Airport, Sawhney buys his ticket; his plane leaves in 15 minutes. "It's a hell of a ride," he says, picking up his satchel. "It's a unique time in history. It's a unique time in academia. And I think I'm in a unique position within that. So we'll see where this all leads."

FEEDBACK: onthejob@fortunemail.com