The Seven Deadly Sins of Product Planning

Marty Cagan argues that a core failure in product planning is that weak projects, which should be killed during product discovery before reaching engineering, often are not. He identifies seven recurring reasons for this inaction and explains that the real cost is less the wasted build than the opportunity cost of what could have been built instead. He frames discovery as a form of farming, where weak ideas must be thinned so strong ones get resources. Ultimately, he places responsibility for killing bad ideas on the executive team, starting with the head of product. The piece matters because it reframes killing projects as a responsibility rather than a failure.

01Key takeaways

• Kill projects lacking evidence of value, usability, and feasibility before they reach engineering.
• Build explicit checkpoints and data-driven criteria so killing a project is a routine decision, not a confrontation.
• Treat stopping a failing project as smart resource allocation rather than personal failure.
• Recognize opportunity cost: bad projects displace good ones that the team could have built.
• Maintain a backlog of validated, worthwhile work so teams are never forced to build something unready.
• Leaders, starting with the head of product, own the responsibility to thin weak ideas and protect strong ones.

02Key sections

Why product planning matters

Cagan describes product planning as the decision of which projects to invest in, spanning strategy, roadmaps, and portfolio work. He notes that every planning process eventually depends on separating good ideas from bad ones.

Projects that should be killed

Projects lacking evidence that they are valuable, usable, and feasible should be stopped before engineering begins. Cagan treats this as the logical outcome of product discovery.

The seven reasons weak projects survive

He lists inertia, denial, pride, abdication, culture, deadlines, and hubris as the forces that keep bad ideas alive. Each reflects a human or organizational tendency rather than a lack of analysis.

Discovery as farming

Cagan compares innovation to farming, where many seeds are planted but weak shoots must be thinned so they do not drain resources from strong ones. Many organizations run too many low-value projects as a result.

Opportunity cost and executive responsibility

The larger cost of bad projects is what the team could have built instead, and the executive team must ensure only strong ideas receive resources.

03From the post

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04Frameworks mentioned

Summary and takeaways written by PM Atlas; quotes are short excerpts. © the original author.