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"I'm getting angry. You won't like me when I'm angry."

That catchphrase from the old TV series "The Incredible Hulk" was usually uttered before the meek scientist David Banner, triggered by rage, turned into a green-skinned, destructive monster.

Customer service representatives, retail clerks and waitstaff are among those who probably wish they had a similar heads-up before things turned nasty. On a daily basis, caught in the crossfire, they take the brunt of abuse from dissatisfied patrons when things turn ugly. The advice typically offered to consumers is that all that yelling and screaming isn't going to help your cause and that calmly stating your case -- by phone, letter or email -- is a better way to resolve a problem.

That genteel advice is well-meaning, but is it always effective? Is getting mad a last resort or a good strategy for getting what you want? Does the squeaky wheel get the grease?

Increasingly, Americans are displaying short attention spans and short tempers.

A Rasmussen Reports poll last August found that 69% of respondents think they and their fellow Americans are "becoming more rude and less civilized."

Poor service gets some of the blame.

The American Express Customer Service Barometer, a study released last month, found that more than half of respondents (56%) admit to having lost their temper with a customer service professional. Consumers age 30-49 proved to be the most frequently angered (61%).

Young people are apparently more patient, with more than half of those age 18-29 saying they've "never lost their temper with a service professional."

Americans who have lost their temper due to poor service express their displeasure in a host of ways, including insisting on speaking with a supervisor (74%) and hanging up the phone (44%). Expletives have crossed the lips of 16% of respondents, with men more likely to use "choice words" (20%) compared with women (12%).

Evidence for why such outbursts may carry some weight is found in another stat American Express researchers believe should be "most unsettling for businesses on the receiving end of customer anger" -- that two in five Americans have threatened to switch to a competitor.

It is not just the loss of one customer that will drive companies to placate red-faced critics. In an age of instant feedback via blogs, tweets and online communities, any complaint can reach the eyes of thousands of people, perhaps inspiring them to weigh in with their own dissatisfaction.

"Americans say they tell an average of nine people about good experiences, and nearly twice as many (16 people) about poor ones -- making every individual service interaction important for businesses," the study says.

Americans also vote with their wallets when they encounter subpar service. In the survey, 78% of consumers have bailed on a transaction or not made an intended purchase because of a poor service experience. On the other hand, the promise of better customer service is a draw for shoppers: Three in five Americans (59%) would try a brand or company for a better service experience.

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Recognizing the need to appease angry customers, and to help keep them calm, Israel-based Exaudios has developed proprietary software that tracks speech patterns and vocal intonations to warn when a caller is about to have a tantrum.

The many concerns about, and efforts to defuse, angry customers means companies are paying attention to all that yelling. The trick, for a consumer, is knowing when to escalate and when to retreat.

For example, threatening legal action will typically trigger guidelines your customer rep has to follow in such cases. The rep will be forced to cut off all conversation and refer you to the business's legal department. Any hope of a speedy resolution is gone at that point.