In Q2 2020, Brian Chesky cut Airbnb's marketing spend from $1.62B to $545M — about $1B gone — and the traffic barely moved. Q4 2020 hit 91% direct/unpaid, and the company IPO'd profitable. The lesson isn't "cut performance"; it's that brand strength sets a ceiling on how much incremental work paid can possibly do, and most attribution systems are designed to obscure that ceiling.

Amazon paused its controversial ad payment change after seller backlash. The real lesson isn't Amazon-specific — it's how to size and hedge platform-policy risk on every channel you depend on.

The 3:1 LTV:CAC benchmark came from mature SaaS at steady state — it wasn't built for the companies quoting it most. Here's the three-gate model that replaces it, and the worked example where a healthy-looking 4.4:1 collapses to a marginal 1.4:1.