Advertising. Some of it is very creative and is done free of cost. Think about the T-Shirts you wear of big brands like Nike, Reebok, and Adidas. They have big logos of their company plastered on them and anyone wearing them is a walking billboard for that company and yet we don't see it this way. Not only we are willing to do this, we are willing to pay the companies in the form of price of that T-Shirt. If I have to wear a shirt that has nothing on it but a huge logo of the manufacturer, I better get paid for it. I guess I am an economic terrorist.