A fact, such as George Washington's birthday or the Pope's address and phone number, is considered synonymous with an idea. It makes no difference how much effort went into discovering a particular fact. Even if it took two years of research to discover a fact, the fact is still not protectable under copyright laws. The blank form is considered to be a type of idea, a conclusion which stems from an old Supreme Court decision. Unfortunately, this test is inherently ambiguous when deciding the scope of copyright protection for certain useful articles.
Some distinctions are clear.
For instance, a painting on the side of a truck is protectable under copyright law even though the truck is a useful article. The painting is clearly separable from the utilitarian aspects of the truck. The overall shape of the truck, on the other hand, would not be copyrightable since the shape is an essential part of the truck's utility. Another commonly considered example is that of clothing. The print found on the fabric of a skirt or jacket is copyrightable, since it exists separately from the utilitarian nature of the clothing.