"Traditional sales and marketing involves increasing market shares, which means selling as much of your product as you can to as many customers as possible. One-to-one marketing involves driving for a share of customer, which means ensuring that each individual customer who buys your product buys more product, buys only your brand, and is happy using your product instead of another to solve his problem. The true, current value of any one customer is a function of the customer's future purchases, across all the product lines, brands, and services offered by you."