Interesting post on "Marketers Out of Touch With Customers", "Over one third don't have a model of their "best" customer or opportunity". Wow! With all the good analytics out there, there just is no excuse for this.
I like to break down customers into three groups -
1) Best Customers - Why are they happy? Keep them happy! Give them more.
2) O.K. Customers - Why aren't they best customers? Change yourself. Give them more.
3) Bad Customers - Help them find your best competitor.