Once we look, we see examples all around us. Thomas Edison's light bulb imitated elements from a dozen earlier bulbs. Shakespeare's "Romeo and Juliet" borrowed from earlier writers, and "West Side Story" in turn drew heavily from Shakespeare. This kind of copying and tweaking often leads to more choice in the marketplace — many variations on a theme — and more competition, which is good for consumers. Copying can also drive the process of invention, as competitors strive to stay ahead. And copying can serve as a powerful form of advertising for originators, one that carries weight because it is authentic. Copying may even expand a market by creating a trend.