(FORTUNE Small Business) – Here's a marketing insight: Teens in Japan dig low riders from Los Angeles. Those who can afford it will buy the souped-up cars and ship them across the Pacific so they can ride through the streets of Tokyo feeling like badass California kids. This is the kind of thing you learn hanging out with LaRon Batchelor, a self-described analyst of the urban marketplace. Batchelor is, in more traditional terms, a youth marketer. This means it's his job not only to be aware of the low-rider phenomenon but also to explain to clients how such juicy factoids could help them sell whatever teen-aimed product they happen to be peddling. He's one of a growing number of men and women who call this a day's work. Their niche: explaining someone else's niche.

Of course, the youth market isn't the small corner it once was. Depending on your definition (most marketers look at 12- to 24-year-olds), that group is more than 50 million strong in the U.S. alone, and last year it spent about $200 billion. So it's clear why an aging executive (someone, say, 40) might be eager to listen to someone half his age with a hundredth of his business experience--especially when the young adviser has grown up on the Internet and knows how to work at Web speed. When Oprah Winfrey's office called teen consultant Kevin Umeh last winter looking for tales of teenage heartbreak, Umeh delivered 50 stories--with names and contacts attached--in a matter of days.

With big corporate money beckoning, the field is getting crowded. "Every 24-year-old who's kind of hip is now labeling himself a trendhunter," complains Jane Buckingham, who produces the popular Cassandra Report and got her start at an ad agency, helping to relaunch a Converse sneaker. But those who rise to the top seem to be the charismatic culture hounds, with chutzpah and business smarts, who can not only take in the scene, but can also make sense of it--something many of them think traditional research firms cannot. "It's not about sending big-ass packets [of data] around the country," says Umeh. "Any human being with an Internet connection can get information. It's telling the story behind the data that counts."

Batchelor, now 30, got a close look at those traditional methods right out of college. He spent a year at Unilever, helping to market I Can't Believe It's Not Butter--an association so uncool he still winces at the recollection. He quit Unilever in 1996 and parked himself in Union Square Park in New York City with a laptop, briefcase, and cell phone (with calls forwarded from a "212" number so no one would know he wasn't in an office). Today Batchelor's two-person company, Star Power, is profitable and bringing in about $1 million in revenues. He now has an indoor office, an accountant, and other trappings of business. And he packages his material, he says, "in a way that's palatable to corporations and [mass] consumers." But he still does no number crunching and runs no focus groups. Instead, he watches the teenagers on Manhattan's streets and sends film crews to more remote spots, such as Amsterdam and South Africa. He sells the video footage to the hip-hop magazine The Source's Website for a nice extra revenue stream. The information helps him consult to marketers or inspires the deals he loves making.

This spring, for example, Batchelor is working with independent film company the Shooting Gallery to market the directorial debut of actor Laurence Fishburne. It's a film that will probably find much of its audience with young African Americans. Batchelor had noticed (mostly by observation at parties or bars) that Hennessy cognac was more popular in that demographic than Seagram's Martell. When he got a tip that Seagram wanted to buff its image, he cold called Martell, suggesting that an association with Fishburne would be a good bet. Martell, happy to borrow some of Fishburne's credibility, signed on.

While Batchelor has kept his operation small, Umeh has taken a different approach. In 1998, he founded Element as a "club" for teens and young adults. He hires cool twentysomethings to cruise kids' hangouts and coaxes recruits to Element's Website (www.elementusa.com), where--with parents' permission--they answer questionnaires about news events, TV shows, and movies. In exchange, members receive a custom-made CD or an online shopping coupon.

Umeh's database has more than 100,000 members, up from 16,000 a year ago. His staff has grown to 30, and clients pay $24,000 a year for his monthly reports. He also does custom work, like answering the call from an Oprah producer one Thursday last winter. Asked for teenage tales of heartbreak, Umeh was able to put out the word on his site, sift through 1,400 responses, and get the kids' permission to use their names--all by Monday. Teens think it's fun to be in on this, says Umeh. "We get thousands of e-mails a week, and a big chunk are thank-yous." Revenues should top $4 million this year. Umeh isn't making a profit, he says, because he's plowing it back in to expand here and overseas.

If these "cool hunters," as they've been labeled, don't sound like their older, more traditional brethren, they don't look like them either. Buckingham, founder of the Cassandra Report and Youth Intelligence, operates out of the basement of a brownstone in New York City's West Village. When her staff--all women--are not jetting off to Detroit or Paris, they bustle about the small, brightly painted office, eating marshmallow Peeps and sidestepping Buckingham's two cats. They work 60 to 80 hours a week, says Buckingham, but they're more likely to be curled up on velvet couches reading a glossy magazine than consulting The Wall Street Journal.

All this might be enough to make the folks over at Roper Starch Worldwide or Yankelovich Partners blanch. These venerable research firms made their names with hard, quantifiable data derived from thousands of face-to-face interviews and focus groups. They crunch, they analyze, they chart, and they churn out reports that weigh more than your laptop. We're the "gold standard" of research, sniffs Carolyn Setlow, a Roper executive who dismisses the idea of any meaningful competition from the teen-watch crowd. "Our strength is not in anecdotal insights."

But Umeh, who counts Conde Nast, Levi's, and ad firm Leo Burnett among his clients, is equally sanguine. Reports such as Yankelovich's Youth Monitor, issued only every two years, can't compete with his. And teens respond more honestly in a Umeh chat room than to an adult with a clipboard, he argues. Besides, says Umeh, "We don't have to prove that we have the data. We're not a market-research company, we're a company that understands Generation Y." He doesn't worry that he'll outgrow his target market. He's willing to change as Generation Y does, bringing in new kids and tweaking his approach to appeal to teens as they become adults. Older folks might not take the time to fill out a questionnaire about their favorite sitcom, but they might want a credit card from a club they grew up with--and be willing to provide the personal data required to get one.

Buckingham, on the other hand, worries. Despite having $3 million in revenues and clients such as McDonald's, she thinks her firm has a broad streak of built-in obsolescence. She's interested in youth, not what follows it. And "I don't want to become one of those people I despise," she says. "If I face executives of a major company talking about teenagers, and I'm not right, I'll feel like an idiot. At some point," she expects, "I'll probably have to abdicate to someone younger."

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