Marginal Revolution reports on one way firms sort their customers out.
When customers call Cingular threatening to switch to another firm or asking for discounts operators see a handy thermometer that tells them the life time value (LTV) of the customer to the company. The higher the meter reading the more discounts the operator is allowed to offer the customer. The Consumerist has the details including excerpts from company documents explaining the system.
Sounds right in my experience. I regularly get $50 out of Telstra by complaining. What does that say about me?