The numbers are kind of staggering. According to the Centers for Disease Control, about 24 million Americans have diabetes, the chronic disease in which the body has a high blood sugar level. That's bad enough for the CDC to call it an epidemic, especially as the numbers have been rising over the last 10 years. As a result, there's a niche in direct mail that has grown a lot in the last decade: marketers trying to help people manage their condition. What immediately stands out about many of these mailings is the copious use of the magic marketing word, "FREE."