I think marketing is a fascinating thing. It's all about influencing the perceptions one has about a certain thing, be it a commercial product or an ideology. Case in point, Jon's example of the brain activity when drinking "cola", Pepsi, or Coke: If a company is successful enough with their marketing campaigns, they they can change the very thought process of a human being using their product. Isn't that cool?
It boils down to my favorite generalization of human behavior: Perception is reality. What does it matter what is real or not real; which reality is the true reality? It doesn't. It only matters how one person or group of people perceives the situation, and that perception is incredibly easy to manipulate.