Consider a cash register receipt coupon offer. For many grocers, back-of-the-till coupon generation is either one size fits all or is based upon a simple Boolean "if the customer purchases A, then offer B" model. For example, customers who buy pasta will receive a coupon for pasta sauce. Customers who buy Brand A pasta sauce will receive a discount coupon for another of Brand A's pasta sauces (or a competing Brand B sauce).

What is still quite rare is for the retailer or sponsoring manufacturer to use past behavior to determine the proper treatment for that customer. If the customer has no history of ever using a back-of-the till coupon or buying pasta sauce, then it is extremely unlikely that the person will do so now.

What if, instead, we actively tracked the pasta buying habits of that customer? Say the customer has a demonstrated behavior of buying five to six pounds of pasta every two weeks and has not purchased pasta in the last 18 days. To bring the person back to the store, we may be better off emailing a coupon (or a double points offer, if the person is not a demonstrated coupon user). Or we could print a coupon for the repeatedly-purchased items that the customer didn't buy, reacting to the behavior that didn't occur.

Of the four tenets of direct marketing—target, offer, creative and timing—getting the timing right—communicating with customers when they are actively "in the market" for a product or service—is a marketer's biggest challenge.

Financial services marketers, dissatisfied with direct marketing response rates that are often lower than 1 percent, have looked for ways to improve the timing on their campaigns. Some strategies have been very effective, such as offering IRAs during income tax season or making student loan offers to a family whose children are college age. What is less obvious is predicting when a customer might be most interested in a home equity loan or an investment account or, even more ominously, understanding when a valued customer is ready to attrite.