Today my family ate lunch at one of our favorite after-church restaurants and I ordered "the usual." This time it wasn't cooked properly. It's a fish dish and initially I thought the fish was bad. Then I realized that the fish wasn't bad -it was still raw (and it's not a sushi restaurant!). Without going into the details, I didn't like the way the restaurant handled my complaint. They handled it poorly. I could have caused a big scene and made demands on the manager and wait staff. Instead I'm choosing to do what will affect the restaurant's bottom line the most - I won't ever go back.
Just because you don't have customers complaining doesn't mean you have happy customers. If customers are yelling at you, at least they are still talking to you and you might have an opportunity to win them back over. And they may even have valid complaints that your "silent but deadly" customers never told you.
Keep this in mind the next time one of your customers gets angry with you.