First, I agree whole-heartedly with everything in that article. Getting new customers to sign up for a service isn't as important as keeping the ones you've got already, and you keep customers by providing them with Grade A service. Treat customers the way you'd want to be treated. It sounds cliche, but it's dead on. If you do have a customer leave your service, always send a final note asking them why they left, if there was something specific they found lacking in your service, something you could have done differently, a feature you should have included, etc, because you're always trying to improve your service. Not all departing customers will bother to give feedback but some will and it's helpful feedback a good percentage of the time.