The idea of revenue churn is startup biz hype. This is how startups play with numbers to make their business seem better than its really doing. You can't make solid business decisions based on a framework of revenue churn since it hides real business issues. The real issue with churn rate is that you have users leaving the service. If you want to better your business you want to reduce this number and get it as close to 0 as possible. Revenue churn would hide this and make it think you're doing well, when in fact you're not. You could be facing a dwindling user base with just a small number of high paying users.