Corn syrup
Corn syrup is a syrup made from maize, composed mainly of fructose. It is used to sweeten soft drinks, juices, ice cream, and many other mass-produced foods. It's liquid form keeps foods moist and prevents them from quickly spoiling. In many areas it is less expensive than sugar due to the agricultural policy, e.g. the United States subsidizes its production while taxing sugar imports, which mainly come from Cuba and other nations.
A variety of corn syrup called high fructose corn syrup is often used to economically improve the flavor of food without increasing costs. The sweetness of high fructose corn syrup masks bitter or otherwise undesirable tastes, allowing companies to use ingredients of substandard quality (i.e. not fresh). This is somewhat similar to historical uses for black pepper.
Corn syrup has been proven have a direct link to the incressing risk of type II diabeties in America.
External link
Is the increased use of high-fructose corn syrup responsible for the rise in obesity? (from The Straight Dope)