“They are not acting like spokespeople, but real people,” Mr. Bernoff said. “You have to be careful about what you say while, at the same time, be much more personal than the average corporate P.R. guy. You need people who understand the mores and etiquette. Not everyone knows how to do that.”

Of course, any new technology has its limits. Twitter, for instance, was not devised to solve complex problems, and companies that tweet too much run the risk of irritating people. “It is not right for saying anything meaningful,” said Paul Gillin, a technology journalist who wrote a book about using social media for marketing. “All anyone has to do is tweet their dissatisfaction and a company will cave in to their demands,” he said. “It does little to encourage loyalty.”

Image @WHIZ Christi Day of Southwest.

At some companies, only those with a bold personality and a dab hand at Twitter need apply. Consider @Christi5321 or, as her friends and family know her, Christi Day, a bubbly 25-year-old specialist in emerging media at Southwest Airlines. “I like to be the center of attention,” said Ms. Day, a former cheerleader. “I was on the dance team at Texas Christian University. I love an audience. I compare Twitter to a bar or a social event.” The people who get the most attention, she said, “have a story to tell.”

At Southwest, a company known for its offbeat sensibility, that story can be as personal as she wants. That means tweeting about the sunburn she got on a photo shoot one recent afternoon. Or responding “yes” to a man who once asked, “Am I the only person who thinks Southwest is overrated?” Ms. Day added: “I have a lot of people Twittering about the celebrities they see on flights. I love celebrity gossip, so I get pretty excited.” A case in point? “Someone just saw Vanessa Hudgens,” she said with a giggle.

“The company has given us freedom to be ourselves,” Ms. Day said of Southwest employees. “As long as I am accurate and on message, I can be as quirky as I am.”