It is segmentation along interest lines. But then they make a major mistake. Of course, some customers have checked more than one category of interest. Having created these segments, they begin to promote them aggressively. The manager of each category promotes like mad, trying to increase profits in the area of his responsibility.
Some customers get one letter a month.
Your best customers are worn down under a deluge of mail. You have worn out your welcome. I never sent more than one a month. But as far as the customers were concerned, they were seeing several a week. They soon learned to chuck them out unread.