We’ve all sat next to that guy, the one who discusses ostensibly “private” information on his cell phone in a public space at a decibel level more commonly found on the average lawnmower.

When you’re that person’s captive—say, because you’re on a packed bus or train with no other available seats—you might even harbor fantasies of exacting some sort of well-deserved revenge.

Well, some people are getting revenge by publishing the details of their loudmouth neighbors’ “private conversations” to their Twitter feeds and other social networks.

Call it “vigilante tweeting.”

Let’s say I’m seated next to a loudmouth attorney on a bus one morning, and he won’t shut up about his latest case. As I’m still wiping the sleep from my eyes trying to have a quiet start to my morning, he’s shouting about his strategy to beat the defendant. I could punish the attorney’s lack of discretion by sending out a “vigilante tweet” containing the lawyer’s name and the details of the case he revealed on the phone.

To be clear, I haven’t done this before (although it’s tempting). But others have.

Rather famously, Peter Shankman, the founder of Help A Reporter Out, was on a train a few years back when a man seated near him pulled out his cell phone and said, “Apologies in advance, I talk a lot.” Shankman sent a vigilante tweet telling his followers that he was going to live stream his seatmate’s entire conversation—and he did, using Yahoo! Live.

Setting aside the legality or morality of making his seatmate the unwitting star of his own Internet show, it’s another instructive reminder of the dangers of speaking too loudly in public space.

This trend has a less invasive, milder form, as well. As an example, I follow a blogger named Eddie Scarry (@escarry), who writes for the website Fishbowl DC. He tweets a regular series called “Eavesdrop Café,” in which he goes to a local coffee shop, listens in on other people’s conversations, and tweets their quotes.

Scarry is more respectful than a true “vigilante tweeter,” since he says he would “never tweet out anything that would explicitly reveal the subject of my tweets.” Rather, he says, “It’s simply a type of voyeurism for my followers.” And, as one of his followers, I can tell you that his #EavesDropCafe tweets are oddly compelling.

The bottom line? Remain aware of your surroundings and your volume. There may be someone within earshot who will capitalize on your obliviousness.

Brad Phillips is author of the new book The Media Training Bible: 101 Things You Absolutely, Positively Need to Know Before Your Next Interview. He blogs at Mr. Media Training, where this story first appeared.

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