Classic marketing is mostly geared towards the idea that 80% of sales come from 20% of top customers. That's called the 80/20 rule. That's why when you walk into two different stores in a mall, they may have slightly different merchandise, but often it is very similar. They are trying to market to the mass of people whose tastes are mainstream and easy to predict, leaving less room for variety and innovation.

In a recession, the 80/20 rule becomes so overwhelming that stores reduce their inventory into very narrow niches in order to market to the customers who are going to buy the more popular items and trends. Anything other than that is seen as a waste of display footage and an increase in rental space costs. This works well for them to keep costs down and sales up.

However, that strategy also leaves a very big opportunity for online marketers to exploit the lack of diversity and novelty in mainstream retail stores by just doing the opposite: marketing to the "long tail."