A man at a tech conference made an off-color joke to a friend; someone overheard, took offense and posted his picture online. A woman posed for a photo making a rude gesture at Arlington National Cemetery and, meaning to amuse her friends, uploaded it to Facebook. Another woman sent out a tweet intended as irreverent satire that came off as racism.

Word spread, posts and photos shared. Next thing you know, these people were facing vilification via Internet – a torrent of criticism, insults and even death threats from around the world – essentially for making bad jokes.

It’s a modern form of punishment that, Jon Ronson argues in “So You’ve Been Publicly Shamed,” is wildly disproportionate to the “crimes.”

An avid tweeter himself, Ronson admits to having gleefully participated in digital pile-ons against errant institutions. But when he noticed ordinary people being targeted, he wondered how they were affected by these outpourings of outrage.

He tracked down the unfortunate souls above, along with author Jonah Lehrer, a once-successful young journalist who was similarly shamed in 2012 when fabricated Bob Dylan quotes were found in his latest book.

To any individual social media user dashing off a disapproving post, it might seem like no big deal, quickly forgotten. But “a snowflake never feels responsible for the avalanche,” Ronson writes. Multiply each individual’s anger by even a fraction of Twitter’s 288 million users or Facebook’s 1.35 billion – not to mention assorted blogs and online forums – and the cumulative effect, Ronson discovers, is brutal.

He finds his subjects demoralized, shattered, worried that their careers and maybe even their lives are permanently damaged. They’ve deleted online accounts and holed up in their houses. All lost their jobs when their companies scrambled to distance themselves. When Lehrer tried to apologize in a public speech, he was made to stand in front of a giant-screen Twitter feed that streamed ridicule as he spoke.

Personable and empathetic, Ronson is an entertaining guide to the odd corners of the shame-o-sphere. He tests theories about what triggers the phenomenon and how a target might cope emotionally. Ronson visits a judge known for handing out zany sentences, like requiring people to carry signs on the street. Surprisingly, these criminals seem better recovered from real-life shamings than Ronson’s subjects from their virtual ones.

The judge notes some differences. For one thing, criminals are guaranteed basic constitutional rights. “You don’t have any rights when you’re accused on the Internet,” the judge says. “And the consequences are worse. It’s worldwide forever.”