But it wasn’t just fun. Metrics were essential to make sure work got done. I tracked people’s participation, and noted when they dropped out of a project. We knew which of our writers got published more frequently. The number of people who opened our e-mails and then took action told me our conversion rates. Our membership was approximately 60 percent Democrat. Women were the majority; their participation on reporting projects never fell below 50 percent. After Bittergate, retired journalists joined OTB in droves.

Each OffTheBus staff member—the professional component of our pro-am formula—also played a specific role. Arianna Huffington and Jay Rosen were our publishers. Marc Cooper, a veteran journalist and a member of the faculty at the USC Annenberg School for Communication, was our editorial adviser. From August 2007 until April 2008, Neil Nagraj coordinated writers and edited copy. Later, editor John Tomasic took his place. In September 2008, we hired Hanna Ingber Win to oversee our features.

As OTB grew, it required the staff to continually restructure and consciously blur that pro-am divide. We invited those who passed an editing test to become op-ed editors.

Citizen journalists, using primarily Twitter, gained worldwide praise for providing the initial bursts of information during the terror attacks last year in Mumbai. But almost a year earlier, in December 2007, Bryan Bissell, an OffTheBus member and a substitute teacher, created a breakthrough moment for OTB and for pro-am reporting broadly.

Minutes after news broke on November 30, 2007, that several staff members in Senator Hillary Rodham Clinton’s campaign office in Rochester, New Hampshire, had been taken hostage, I tapped our database to find our contributor nearest to the scene. It was Bissell. Two hours later, when school let out, he raced over to the headquarters. By then, Fox News had named Troy Alan Stanley as the hostage-taker. The police had cordoned off downtown Rochester, and reporters were camped outside the campaign office. We found Stanley’s home address and sent Bissell to his neighborhood.

When Bissell arrived at Stanley’s building, there were no police and the super’s wife insisted that Stanley was innocent. “Stanley walked into his apartment not two minutes ago,” she told him. Bissell then talked to Stanley, who said he had only just learned of the hostage situation. Less than two minutes before we published our story, Fox News issued a correction. Bissell not only demonstrated how HuffPost could do much more than aggregate existing news reports, he also did what citizen journalists in Mumbai did not—advanced a story beyond the Web’s organic happenings.

It was an important early milestone in helping us understand what we could do with OTB. Initially, we had two main strategies for producing our journalism: we recruited and mentored citizen journalists who could independently write and report, and took on stories using collaborative-reporting methodologies in which a network, not an individual reporter, breaks news. This is both revolutionary and not. Major metro dailies like The New York Times often publish stories that draw from reporting by a half dozen or so reporters and stringers around the country. OTB stories were like that approach on steroids, with twelve thousand reporters and stringers, albeit unpaid volunteers, to draw from.

The first strategy—recruiting and mentoring citizen journalists—was by far the most time-consuming, costly, and risky. We struggled for months to build a cadre of committed writers who could carry the publication. We invested most of our editorial resources in fact-checking, editing, reworking leads, and providing guidance. The ideal of a citizen journalist bequeathed to us by new-media evangelists both inspired and got in the way. Incoming writers had great expectations, like beating The Associated Press to a scoop. They raced to put out copy only to realize the story already sat on HuffPost’s homepage. Ultimately, many more felt comfortable being impressionistic, profiling their and their friends’ experiences around the campaign. They resisted hard leads. We risked becoming the Monet School of Journalism. This forced us to redouble our efforts to nudge and teach writers how to produce the sort of reliably reported coverage we desired. We had to create and sustain a strong reporting culture, and that meant slower growth to start, and lots of editing.

Amanda Michel directed OffTheBus, and is now the editor of distributed reporting for ProPublica, the nonprofit investigative journalism outlet based in New York.