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(CareerBuilder.com) -- Have you ever received poor service from someone you expected should be helping you as part of his or her job?

The answer is almost certainly "yes."

And, if you're like most people, you have probably also experienced the frustration of working with someone who made your own job more difficult.

In both cases you may have wondered, "Why don't they just fire this person?"

Firing someone may seem easy in theory, but it is often a last resort for an employer.

A bad employee's supervisor may know that the employee isn't performing up to snuff, but that supervisor -- or the company -- may have what they consider to be a good reason for not firing the employee.

Whenever you encounter someone who you think deserves to be fired -- either in your own workplace or elsewhere -- consider if any of the following might be the reason the bad employee is still on the job:

1. The employee has a relationship with someone higher up.

A relationship doesn't necessarily have to be romantic or family, although either is a possibility. In many cases, the relationship that keeps someone from getting fired is friendship.

The bad employee may not perform well on the job, but may be a golf or drinking buddy for your boss, or may simply be someone that senior management enjoys having around the office.

2. The boss relies on the employee.

According to Terence R. Mitchell, Ph.D., author of the business text "People in Organizations: Understanding Their Behavior," when a supervisor depends on an employee, the supervisor is less likely to attribute poor performance to the employee's ability or attitude, and more likely to attribute the poor performance to forces beyond the employee's control.

3. The employee brings more value to the company than he or she costs.

Maybe the employee who jokes around and wastes other employees' time at meetings is also a brilliant worker whose productivity has resulted in significant revenue for the company.

4. The boss thinks it could be worse.

Even if everyone knows the employee is not pulling his or her weight, management may fear that a replacement could do an even worse job. This fear is compounded if the company has previously had other people perform more poorly in the position.

5. The boss is afraid of the employee.

If there are concerns that an employee might sue the company or possibly become violent if fired, it may take longer to let that employee go. If there's a threat, the company needs to consult with legal or security experts and put appropriate measures in place before letting a bad employee go.

6. The boss feels sorry for the employee.

In such cases, a boss is sympathetic to the employee, and not to those whom the employee's actions may be hurting.

The boss may worry that if the bad employee is fired, he or she won't be able to find another job. If the employee needs the money to support a family, has health problems, or has recently experienced another life challenge, the boss may feel it's best to let the employee keep the job.

7. The boss doesn't want to go through the hiring process.

It takes time to review applications, conduct interviews, check references, and train a new person. The boss may believe it's easier to deal with the consequences when the bad employee messes up rather than deal with hiring a replacement.

8. The employee knows something.

The employee might know something embarrassing about the boss, but it's more likely he or she simply knows historical information that the company needs today. For example, if the employee is the only one who knows how to operate an ancient piece of equipment that the company still uses, your employer may need to keep the employee around.

9. The employee has everybody fooled.

In their book "Snakes in Suits," Paul Babiak, Ph.D. and Robert D. Hare, Ph.D., explain that a surprising number of workplaces employ psychopaths.

While psychopaths make up 1 percent of the general population, Babiak and Hare found that 3.5 percent of the executives they worked with "fit the profile of the psychopath."

Psychopathic employees are pathological liars who get away with doing little or no work. They charm senior management with their "leadership potential," con co-workers into covering for them, and successfully blame others for their mistakes.

If you're the only one who sees what they're up to, you're in a tough spot. Sometimes it's the whistle-blower who gets fired, not the snake.

10. He or she is not really a bad employee.

So what if a co-worker sometimes works from home, takes long lunches, or does something else you don't think is fair -- as long as his or her work gets done.

If you're not the supervisor, you're not personally affected, and the employee is not hurting anyone such as customers or co-workers, stop stressing over what he or she does and focus instead on your own work. E-mail to a friend

Copyright CareerBuilder.com 2009. All rights reserved. The information contained in this article may not be published, broadcast or otherwise distributed without the prior written authority

Tag Goulet is co-founder of FabJob.com, a publisher of career guides offering step-by-step advice for breaking into a variety of dream careers. Visit www.FabJob.com to subscribe to the free career newsletter.

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