There's an expression common in high-tech companies that product designers should "eat their own dog food," a.k.a. "dog fooding." The idea is that if companies use their own products, they're more likely to ensure those products are usable.

While "dog fooding" sounds like common sense, it's not that great an idea in real life, because it tends to result in product designs that make sense to the designers rather than to customers.  

When confronted with a complex product, users automatically create a mental, conceptual model of how they behave, and then make decisions about how the product should behave based upon that conceptual model.

A new user approaching a finished product for the first time will almost always construct a conceptual model that's quite different from the model that drove the design. What makes sense to an engineer might not make much sense to a non-engineer.

This occurs all the time in consumer electronics. There are millions, perhaps billions, of devices that still have a piece of electrical tape covering up a flashing display because it's nearly impossible for a non-engineer to figure out how to set the time.

Over the past few months, my wife, a music teacher, has been struggling to learn various "online learning" applications. She quickly and sadly realized that such products, rather than reflecting how a teacher thinks, invariably reflect how a programmer thinks.

The problem with dog fooding is that it encourages designers to think of themselves first and customers second. Such designers often expect customers to learn to think like engineers, in which case, they'll understand the product.

Dog fooding also extends itself into how companies market. A common manifestation are product demos that go through a product's features one at a time, and marketing materials that list a product's features without any context. In both cases, little or no thought has gone into how a customer might want to use the product or what they might use it for.

Dog fooding thus tends to reinforce an "insider's" view of how a product should work rather than encouraging designers to take the extra time and effort to design products that make sense from the viewpoint of an average user.

Put another way, "eat your own dog food" all too easily devolves into "breathe your own exhaust."