Consumers have always had relationships with brands, but sophisticated tools for analyzing customer data are finally allowing marketing organizations to personalize and manage those relationships. With this new power comes a new challenge: People now expect companies to understand what type of relationships they want and to respond appropriately—they want firms to hold up their end of the bargain. Unfortunately, many brands don’t meet those expectations.

A version of this article appeared in the July–August 2014 issue of Harvard Business Review.