You know that hollow feeling when you're talking about something you care very much about, and someone's eyes just wander off. They're not listening. They don't care. They are underestimating you, and you know it.

When he was seeking venture funding for his grooming products startup, Walker and Company, Tristan Walker pitched an investor whom he says he respected greatly. When he showed her a slide of his product--a razor kit for people with coarse or curly hair--next to a common acne medication, to illuminate the size of his market, she scoffed. She said she couldn't believe that the problem of razor burn and bumps could be anywhere near that of acne.

He knew otherwise: His research showed that among black men in particular, these were serious issues.

"The thing that was most frustrating about my round of fundraising was that people let their lack of context cloud their judgment," he said. He could forgive this woman for not knowing much about skin-care issues for people of color. But he knew his idea had been underestimated.

Walker told the story to an audience of a couple hundred people at the Fast Company Innovation Festival Monday. Next to him onstage was Katia Beauchamp, the co-founder of Birchbox, a beauty company that began by selling a monthly subscription to a selection of beauty-product samples.

When she and her co-founder created Birchbox in 2005, there were plenty of doubters--investors, quite logically, wondered why people would pay for samples that have always been free. After being turned down for funding repeatedly, Birchbox racked up subscribers extraordinarily quickly, meeting its five-year goals in seven months.

Looking back, Beauchamp says she's grateful for the experience of facing so many skeptics. "I think the incredible thing about being underestimated... it's a huge blessing. It teaches you to work insanely hard, and it teaches you to pitch to people who doubt you."

The hard work has paid off, of course: Her company has raised $72 million in venture-capital investment, has nearly 300 employees, over 800 brand partners, and more than a million subscribers.

Chad Dickerson, the chief executive of Etsy, was also on stage. Despite the fact that he runs a now publicly traded company that's also a community of 1.5 million craft-sellers, he says he still gets underestimated. He recounted the time a journalist asked him: "Isn't Etsy just women?"

The answer is, of course not. Even so, Dickerson found himself thinking, wait, why would that be limiting?  "Yeah, 50 percent of the world's population, who control all of the discretionary spending?"

Walker's company's demographic is arguably even larger, he said. "People of color--that's most of the world, that's not niche."

For his part, Walker doesn't always try to school the disbelievers. He said there's some value, when you're just starting out building a company, to keeping your head down and not attracting every flash bulb of attention. As soon as there is widespread attention, he and Beauchamp agreed, there are copycats.

"As long as people continue to believe it is 'niche,' we will keep flying under the radar," Walker said. "And just doing what we do best."

And he hasn't been doing so badly: Walker and Company employs 20 people, has more than $30 million in venture-capital investment, and will soon have a product on the shelves of Target stores. If that's his definition of "under the radar," it's not going to apply for too long.