Marketplace covered the acquisition of Duane Reade by Walgreens and suggested that drugstores in New York are on nearly every corner because consumers seek convenience. That’s true, but to really understand why they are all over, you need to understand a little game theory. Presh over at Mind Your Decisions has a very simple explanation of why competing gas stations are found across the street from each other and, similarly, why political candidates tend to be centrists.