Terrific post. Thanks for contributing to this discussion. I teach this topic in my Harvard Business School class (www.hbsltv.com) and point them to the fact that in addition to your excellent points, LTV/CAC math must be more realistic — LTV math is often wrong ( https://seeingbothsides.com/2015/10/24/your-ltv-math-is-wrong/) and CAC math often gets worse over time ( https://seeingbothsides.com/2015/02/09/why-metrics-get-worse-with-scale/). These are two areas where I observe entrepreneurs being consistently overly optimistic.