Interesting post by John Sviokla on why you should not just use past behavior to determine which customers are most valuable to you, but rather look to their potential as well.
My favorite quote
Most CRM does not focus on the future, and potential. Worse yet, those firms that are poor at becoming the dominant supplier may in fact reward internal behavior that is incremental. You might be growing an account, but losing market share. This means that the competition will grow even faster than you, and you will never become the dominant supplier of the category you service.
Do you predict the potential lifetime value of your customers? If so, at what point in the buy cycle?