On July 1, Seth Bannon appeared before several hundred techies and investors at the New York Tech Meetup, the industry gathering where Tumblr and Foursquare made their debut.

Even among this pedigreed audience, Bannon inspired great interest. The company he founded in 2010, now known as Amicus, had raised nearly $4 million from investors and was the rare start-up that made money while doing actual good, helping nonprofits like the AFL-CIO and the Texas Democratic Party mobilize supporters. An Obama campaign alumnus, Bannon frequently appeared on panels at conferences like South by Southwest. He inspired mentions not just in tech publications, but in business and general-interest outlets like The Economist and The Atlantic, which gushed that Amicus had “helped activists in Minnesota and Washington win same-sex-marriage campaigns.” In 2012, he and his co-founder Ben Lamothe were named to the Forbes “30 under 30” list of social entrepreneurs.

Bannon, decked out in jeans, a brown T-shirt, and de rigueur beard, took the opportunity to introduce his company’s latest product—a tool that allowed supporters of nonprofits to send customized, tangible postcards to their friends on the organizations’ behalf. He began to move through his slides, showing how the card was constructed with a succession of clicks. “I can even flip the post card over to see the front artwork. In this case”—he paused so the crowd could laugh at a picture of baby badgers that flashed on the screen—“Yeah, exactly. You’re giving money.” Before wrapping up, Bannon made a special announcement: Over the past three years, Amicus had only worked with nonprofits. Now, for the first time, for-profit companies could enlist its help, too. “If any of you want to use it, go to amicushq.com/nytm, and you can jump to the head of the waiting list,” he said.

Every successful startup is in some sense a confidence game. Any founder who told the literal truth about the frenzied ad-hockery of launching a company would scare away customers and investors and quickly be out of business.

Even by the standards of this world, however, Bannon was engaged in some rather brazen frontsmanship. In early June, just a few weeks before he took the stage, Bannon revealed to his co-founders that Amicus owed the IRS roughly half a million dollars because it hadn’t paid payroll taxes for several years. Though Bannon, who as CEO chose to have sole responsibility over the company’s financials, had been alerted to the oversight months earlier, he never disclosed the information to the rest of the company’s leadership. It was not until his two co-founders, Topper Bowers and Ben Lamothe, caught wind of the problem on their own that they finally pried it out of him. “My initial reaction was numbness, shock,” says Bowers, one of a dozen former colleagues who spoke with me. (Bannon himself declined to comment.)