This document discusses customer lifetime value (CLV), which is the net present value of future cash flows from a customer. It notes that not all customers are equally profitable and that customer retention can be cheaper than acquisition. Common CLV modeling approaches discussed include RFM analysis, the Pareto/BG-NBD model, and random forest models using features like customer engagement levels. Case studies on Groupon and ASOS are provided that used random forests and neural networks to predict churn and CLV. While neural networks can improve predictions, random forests often provide good results at a lower cost.