The world's oldest industry is gorged with unsung heroes. Some service-industry professionals are the closest I've come to communing with saints.

As of 2009, about 10 percent of the population of the U.S. is employed by the restaurant industry. I defer to career servers with my tail between my legs, knowing that they're frequented by patrons who expect both levity and laser vision, served with a side of psychic intuition and a smile, while still managing to up-sell enough to keep their bosses happy — and balancing trays of Riedel stemware without losing any to the floor.

Where I grew up, it was standard practice to tip baggers at the grocery store. Now, I always feel conspicuous and a little uncomfortable when I don't. When it comes to tipping, to what degree do we let our discomfort dictate our actions, and where do we draw the line?

I felt a little disgusted with myself after a recent dinner with terrible service at a local sushi restaurant.

"Why am I incapable of tipping under 20 percent?" I asked my friend.

"Because you've been on the other side of the fence," he said.

But he was wrong; that's not the reason. I've browbeaten myself into gratuity paralysis, held hostage by my own habits. I also don't send food back, a self-defeating policy bred from years of misguided thinking that the only thing lamer than a disappointing plate of food is not eating it.

In Japan, there are rare circumstances under which a tip is appropriate, and the end of a meal isn't one of them. Instead, servers take a certain pride in their establishment, and ideally that gets transferred to the diner as part of the experience. My auto mechanic in Santa Fe adopts a pride and work ethic similar to the Japanese when it comes to his business. Should I be thinking about tipping him?

Some people prefer to go the way of the French, with service charges included, an Old World approach that helps to preserve more distinct boundaries between servers and patrons, but is antithetical to the more familiar meritocratic concept of tipping to inspire better service. But what if our capitalistic, motivational, incentive-based approach to tipping says something about our lowered expectations?

What if we took that same system and applied it to the chef who forgot to change the fat in the fryer, resulting in my plateful of inedible onion rings, or another who changed suppliers and ended up with fatty, gristly steaks that bore no resemblance to gorgeous ones eaten previously at the same restaurant? Extending that line of logic a little further, if a flight I'm on has been delayed or canceled, should I expect to be refunded or otherwise compensated because I didn't get to my destination on time? It's a sad day when everything has to come with an attached disclaimer, but there are times when I just want to clutch my wallet to my chest and say, "You can't really expect me to pay for that. Come on!"

Nevertheless, don't shoot the messenger. In extreme cases of an unsatisfactory experience, regardless of whether or not it's service-related, some people will show displeasure by leaving a penny, but I'm horrified whenever withholding a tip is done to expresses dissatisfaction with a service that has a narrower girth for personal error than most people realize.

In any industry or region where tipping is common practice, it is occasionally accompanied by the expectation that anything can be accomplished with an attractive sum of cash. And those expectations can range from innocuous (handing the valet an extra $10 to plant a rose for your date on your dashboard) to vulgar (use your imagination).

I've heard arguments from those who believe that tipping is optional. Well, in the U.S., it's not. The success of a restaurant (or any business, really) often hinges more heavily on great service rather than a great product. In my fantasy world, nobody would ever go hungry — and nobody would ever be shortchanged on a tip. Sometimes, without clear-cut guidelines on tipping, things can get confusing. At the end of the day, though, if you can't afford to tip 20 percent on great service, then you probably can't afford to eat out.