Earlier this month during a presentation, a participant posed the following question:

“What difference does it make if one customer leaves dissatisfied when there’s a line of customers waiting to take his place?”

Having worked in high-volume environments in New York City and Orlando, I’ve detected this sentiment—if not heard this same question—from frontline employees who took for granted that there would always be a line of customers waiting to hand over their money.

Some employees are fortunate to work in bustling environments where demand is strong and customer volume is high. Such operations often charge price premiums and realize solid profits.

Consider the hostess at a swank downtown restaurant requiring reservations. The entrance is standing room only and there’s a month-long wait to secure a table for dinner. And imagine the movie theatre employee working behind the concession counter, staring out at a sea of anonymous customers in the minutes leading up to the start of the latest blockbuster.

Because their products or services are in demand and profitable, employees in these establishments may rationalize that if they lose a dissatisfied customer, they will make up for the lost revenue on the next customer (or 10 customers) in line.

This rationale is flawed, fuels arrogance, and produces attitudes of indifference toward customers and entitlement to their spending.

What these employees fail to recognize is that, regardless of demand, individual customers are irreplaceable.

I first read this notion in the outstanding book, Exceptional Service Exceptional Profit by Leonardo Inghilleri and Micah Solomon

Conventional thinking about customer retention is that customers are replaceable. That is, when one customer leaves, another customer will take his place.

But the authors are not talking about the anonymous masses. They are talking about the dismissed couple who was admonished by the condescending hostess because they lacked the foresight to reserve a table in advance at such a popular restaurant. And they are talking about the frustrated moviegoer who, after waiting a full five minutes in a line that failed to move, chose to skip the buttered popcorn and Coke so he didn’t miss the dramatic opening scene.

If the dismissed couple and the frustrated moviegoer are not satisfied with their experiences, they may choose to defect to other providers in search of more flexibility, responsiveness, respect, efficiency, or a number of other factors. And because a majority of customers do not complain—you may never know that they left or why they left.

And here’s the scary part: The admonished couple and the anonymous moviegoer are irreplaceable.

When they decide to quit doing business with you, they mean it. So, even if you attract a new customer’s spending, you won’t receive another nickel from these three individual customers ever again.

Recognize that when an individual customer defects, he or she is irreplaceable. And his or her lifetime contribution to your business—including future spending, feedback, and referrals—cannot be replaced. Never. Ever. Forever. And forever’s a long time.

How would you respond to the opening question?

Because of my work in the field of hospitality, I read quite a few books on the topic of customer service and thanks to great authors like Chip Bell, Scott McKain, Colin Shaw, and others, I always complete a book more prepared to serve my own clients.

Recently I was reading a book by Leonardo Inghilleri and Micah Solomon titled, Exceptional Service Exceptional Profit. I had already underlined several refreshing insights when, on page 43 of the book, I highlighted this sentence:

Individual customers are irreplaceable.

I was so energized by the sentence that I called to my wife in the other room to share it with her.

Conventional thinking about customer retention is that customers are replaceable. That is, when one customer leaves, there’s always another to take his or her place.

But the authors are not talking about the anonymous masses. They are talking about Mr. Lewis in room 512 who cannot access the Internet, Ms. Connor who’s been on hold with technical support for seven minutes (and counting…), and Mr. Garcia who is challenging an unexpected split plate charge on his check at table 17.

If Mr. Lewis, Ms. Connor, and Mr. Garcia are not satisfied with their experiences, they may choose to defect from one provider to another in search of improved quality, responsiveness, value, or a number of other factors. And because a majority of customers do not complain—you’ll never know that they left or why they left.

And here’s the scary part: Mr. Lewis, Ms. Connor, and Mr. Garcia are irreplaceable.

When they decide to quit doing business with you, they are gone. Forever. You may attract a new customer’s spending but you won’t receive another nickel from these three individual customers. Ever.

A great illustration of this truth is the cable industry. In 2006, cable TV companies had 68.5 million video customers. The number fell to 63.3 million in 2009, according to research firm In-Stat.

Why did cable customers defect? To save money? To get better quality? Or were they just tired of waiting for the cable guy to arrive between the hours of 9am to 1pm?

How much revenue does each customer represent to the cable company? My last cable bill was $119.79. That’s $1,437.48 per year. At that rate, my lifetime value to my cable company is significant.

Calculate the lifetime value of your own customers. Given that total, can you really afford to lose even one because of a lapse in customer service?

Recognize that when one of your customers (e.g., Scott Lewis or Jill Connor) defects, he or she is irreplaceable. And his or her lifetime contribution to your business—including future spending, feedback, and referrals—can never be replaced. Ever.