Imagine a row of cramped stalls on the dusty road somewhere in the Middle East, several hundred years ago. The stalls sit side-by-side on both sides of a dusty street. Some people in the crowd are simply going from one place to another, and some have come to purchase a particular item. The vendors use all sorts of schemes and strategies to get the attention of the passersby and draw them to their own stall rather than to their neighbor’s.