In the early days of Twitter, I was a keen shamer. When newspaper columnists made racist or homophobic statements, I joined the pile-on. Sometimes I led it. The journalist A. A. Gill once wrote a column about shooting a baboon on safari in Tanzania: “I’m told they can be tricky to shoot. They run up trees, hang on for grim life. They die hard, baboons. But not this one. A soft-nosed .357 blew his lungs out.” Gill did the deed because he “wanted to get a sense of what it might be like to kill someone, a stranger.”

I was among the first people to alert social media. (This was because Gill always gave my television documentaries bad reviews, so I tended to keep a vigilant eye on things he could be got for.) Within minutes, it was everywhere. Amid the hundreds of congratulatory messages I received, one stuck out: “Were you a bully at school?”

Still, in those early days, the collective fury felt righteous, powerful and effective. It felt as if hierarchies were being dismantled, as if justice were being democratized. As time passed, though, I watched these shame campaigns multiply, to the point that they targeted not just powerful institutions and public figures but really anyone perceived to have done something offensive. I also began to marvel at the disconnect between the severity of the crime and the gleeful savagery of the punishment. It almost felt as if shamings were now happening for their own sake, as if they were following a script.

Eventually I started to wonder about the recipients of our shamings, the real humans who were the virtual targets of these campaigns. So for the past two years, I’ve been interviewing individuals like Justine Sacco: everyday people pilloried brutally, most often for posting some poorly considered joke on social media. Whenever possible, I have met them in person, to truly grasp the emotional toll at the other end of our screens. The people I met were mostly unemployed, fired for their transgressions, and they seemed broken somehow — deeply confused and traumatized.

One person I met was Lindsey Stone, a 32-year-old Massachusetts woman who posed for a photograph while mocking a sign at Arlington National Cemetery’s Tomb of the Unknowns. Stone had stood next to the sign, which asks for “Silence and Respect,” pretending to scream and flip the bird. She and her co-worker Jamie, who posted the picture on Facebook, had a running joke about disobeying signs — smoking in front of No Smoking signs, for example — and documenting it. But shorn of this context, her picture appeared to be a joke not about a sign but about the war dead. Worse, Jamie didn’t realize that her mobile uploads were visible to the public.

Four weeks later, Stone and Jamie were out celebrating Jamie’s birthday when their phones started vibrating repeatedly. Someone had found the photo and brought it to the attention of hordes of online strangers. Soon there was a wildly popular “Fire Lindsey Stone” Facebook page. The next morning, there were news cameras outside her home; when she showed up to her job, at a program for developmentally disabled adults, she was told to hand over her keys. (“After they fire her, maybe she needs to sign up as a client,” read one of the thousands of Facebook messages denouncing her. “Woman needs help.”) She barely left home for the year that followed, racked by PTSD, depression and insomnia. “I didn’t want to be seen by anyone,” she told me last March at her home in Plymouth, Mass. “I didn’t want people looking at me.”