One of my favorite new career bloggers, Nadira Hira at Fortune, posted a cautionary tale from 30,000 feet.  Nadira was on a 7 a.m. flight from New York to Virginia when a perfectly normal-looking, well-dressed, twenty-something man of corporate mien began chatting with his coworker in a voice only an arena crowd could love.

He shouted the entire two-and-a-half hour flight, while the other passenger simply nodded and interjected a question now and then. The dozen or so people on the small plane shot him periodic glares, sighed audibly in his direction, and fussily draped all manner of paper and pashmina over their faces.  Sadly, he was oblivious.

Nadira learned all sorts of interesting facts, including details about ongoing high-level negotiations at his firm, the visa status of his visiting colleagues, and the salaries of just about everyone he knew. She and her fellow passengers also heard about the guy’s efforts to secure work-abroad papers and circumnavigate pesky new regulations, as well as his fascinating views on success: “I could be making $500 an hour,” he yelled, “but then I’d be responsible for s–t.”

Folks, your corporate persona, or the mature, professional and competent face you project to the world, isn’t something you turn on for the boss or other VIPs who happen to be around.  Whether you’re in the company cafeteria or in the bar down the street from your office, you’re in public, and you must assume that people are listening to what you’re saying.  Always be professional and courteous, and if the information is confidential or the tone is obnoxious, save it for the privacy of your home.  You never know when a top-notch reporter, or even just a regular guy with some damaging connections, is sitting next to you.