When I asked Craig Finlay how Facebook became a major lead generator for his wedding photography business, he interrupted me mid-sentence. “It’s not a major lead generator,” he said. “It’s the entirety of the business.”

Finlay’s experience is a neat case study in the power of social marketing. Up until 2010 or so, photography had been mostly a hobby. He was an avid practitioner of urban exploration, a term for photographers who enter — oftentimes illegally — abandoned buildings and urban structures to photograph their interiors. I accompanied Finlay on one of these trips in 2009, sneaking into a small-town Illinois college that had been abandoned for more than a decade. The experience had been surreal, and I stood back as Finlay methodically moved from room to room, snapping pictures of classrooms that seemed to have been evacuated suddenly without any regard for what was left behind. In the basement, we even found a still-lit lightbulb hanging above a few feet of standing water. (“The thing about buildings like these, sometimes they want to sell them so they never disconnect them from the grid,” Finlay said. “It’s just considered vacant of occupants.”)

Every person who was at the wedding was promoting Soda Fountain Photography’s content to their social graph.

Finlay worked as a reporter for a small daily paper in Illinois for a year, and in his capacity there he regularly took photographs. For the the most part his hobby remained unpaid — an increasingly expensive ordeal. The notion of making money from it came from his wife Mysi, who had moved with him to Bloomington, Indiana in early 2009. “It grew out of a conversation I had with Mysi while I was just sort of going through and cleaning all of my camera gear,” Finlay recalled. “I had it lying on the table and she just idly wondered how much money I had invested in all this camera gear. I think I had like $5,000 in gear just lying around, and she had the idea that, I don’t know, maybe we should start recouping some of those costs.”

Settling on shooting weddings was the obvious choice; Finlay was partway through a PhD in information science at Indiana University*, and weddings wouldn’t conflict with his schedule, as they often occurred on weekends. The first few weddings, however, didn’t generate much revenue. Finlay shot one friend’s wedding for free as a wedding gift; another wedding the couple photographed for only $200. But the latter one they did for a friend of Mysi’s mother, a woman who happened to be a hair dresser. “It turns out if you ever work as a wedding vendor and have an opportunity to do a favor for a hairdresser, always do so,” he said. “It’ll pay dividends.”

That’s because wedding photography is, in essence, a profession that’s based almost entirely on word-of-mouth. One wedding leads to another, which leads to another. Slowly, the Finlays began to pick up more gigs, though for the most part they were done on the cheap for friends within their social circle. The wedding that changed all that was one the couple shot for a girl, Rebecca, with whom Mysi had gone to high school. “It turned out that all of her bridesmaids were engaged or about to get engaged,” he said. “And so it started this whole chain of Rebecca-referred weddings. And that’s how this Facebook thing started, too.”

The way Finlay described “this Facebook thing,” it seemed like it had occurred mostly on a whim. He and Mysi had been editing photos from Rebecca’s shoot and decided to throw some of them up onto the Facebook page they had created for their company, Soda Fountain Photography. They tagged the bride and the groom in these initial photos and went back to editing the rest of the batch. But a curious thing happened: When the photos hit the bride and groom’s Facebook walls, friends who had attended the wedding started going in and tagging themselves, thereby publishing the photos to their friends’ walls. In essence, every person who was at the wedding was promoting Soda Fountain Photography’s content — each picture with the company’s watermark at the bottom — to their social graph.

In a little over a year, the couple has turned a hobby into a six-figure business.

“Almost immediately, our clients were being generated on Facebook,” Finlay recalled. “Because there were the people in the wedding who were getting tagged, and I guess the fortunate thing about wedding photography is that the friends of your clients are the demographic you’re always trying to hit. They’re 20-somethings, and they’re either getting engaged or are engaged. So when you take photos and throw them up on Facebook, you tag the bride and the groom, and, yeah, a lot of people looking at the album are family members, but a lot of them are their friends too, and the people who are engaged really interact with your photography in a much deeper way than they could with just a pretty ad in a magazine. They’re clicking through dozens of photos that you immediately throw up on Facebook from the wedding and they don’t think they’re looking at an advertisement — they just think they’re looking at their friends’ wedding photos. But every photo has a watermark on it, so every time you look at it it’s like it’s being imprinted.”

Soon, it became the standard operating procedure to throw up a “sneak peek” Facebook album of between 40 and 50 photos after every wedding. If a wedding occurred on a Saturday then they would rush to have the initial photos up on Facebook by Monday at the latest. The number of referrals they received as a result of this strategy was overwhelming.

Since that initial lightbulb experience, the couple has done little to change their initial tactics: They publish the sneak peak to the Facebook page, tag the bride and the groom, and let the rest take care of itself. “You open up your email and it says, ‘So and so tagged eight photos of you,’ and you think, ‘those must be the pictures from the wedding.’ So you start going through it and tagging your friends.”

In fact, Finlay said, “Facebook is actually reaching out on our behalf to these people and telling them to look at the photo that they’ve been tagged on — a photo with our watermark — and then they can click around and the option to contact us is right there.”

It’s not even December yet and Soda Fountain Photography is already booked for the entire wedding season next year — 25 weekends in all. And because of the rise in demand, their prices have increased. Early on, they were charging less than $800 for a wedding. These days, Finlay said, most of their clients choose a $3,500 package. In a little over a year, the couple has turned a hobby into a six-figure business.

And nearly all of those leads were generated through Facebook. Finlay still seemed perplexed at how easy it was. “It’s as if someone designed a program solely for generating photography leads.”

*Update: This post initially listed Finlay’s alma mater as the University of Indiana. We’ve updated it to reflect the school’s proper name, Indiana University.