No one wants to be on the receiving end of continual, impersonal communications.  When you target a specific segment of customers with smaller campaigns, the cumulative revenue is much greater than that of a "spray and pray" blast email campaign. And the more you cater to increasingly refined segments, the average uplift you gain from your total customer base grows—as does the average uplift from each individual customer. Article: Eight Steps to Leave Blast Emails Behind and Launch Intelligent Communications Instead