The static size of a Total Addressable Market (TAM) is a misleading metric for big ideas. A better evaluation framework focuses on two questions: Will the product's innovation cause the existing TAM to grow multiple times over? Can the company layer on additional, new TAMs over its lifetime?

Initial data suggested the market for design tools was too small to build a large business. Figma's founders bet on the trend that design was becoming a key business differentiator, which would force the market to expand. They focused on building for the trend, not the existing TAM.

For AI companies experiencing explosive growth like Harvey (tripling ARR in a year), traditional TAM analysis is an obstacle, not a tool. Such growth signals the company is capturing a new budget pool (e.g., labor costs) that dwarfs the existing software market. In these cases, the revenue trajectory itself becomes the best indicator of the true TAM.

Founders in deep tech and space are moving beyond traditional TAM analysis. They justify high valuations by pitching narratives of creating entirely new markets, like interplanetary humanity or space-based data centers. This shifts the conversation from 'what is the market?' to 'what could the market become?'.

Vanta effectively segments the market by product experience. Startups, unfamiliar with compliance, need a guided, prescriptive "TurboTax-like" process. In contrast, mature enterprises want a monitoring platform—"DataDog for compliance controls"—to manage their existing, complex programs.

Traditional market sizing, which analyzes existing demand, is useless for true technological breakthroughs. A fundamental change on the supply side (e.g., GPUs for AI, cloud for software) unlocks markets that are orders of magnitude larger than their predecessors (e.g., gaming, on-prem software).

Analysts often mistakenly constrain a disruptor's potential to the size of the existing market it's replacing (e.g., valuing Uber based on the taxi market). Truly disruptive products create entirely new behaviors and expand the total addressable market (TAM) by orders of magnitude, a key insight for valuing high-growth companies.

Companies like Amazon (from books to cloud) and Intuitive Surgical (from one specific surgery to many) became massive winners by creating new markets, not just conquering existing ones. Investors should prioritize businesses with the innovative capacity to expand their TAM, as initial market sizes are often misleadingly small.

When evaluating revolutionary ideas, traditional Total Addressable Market (TAM) analysis is useless. VCs should instead bet on founders with a "world-bending vision" capable of inducing a new market, not just capturing an existing one. Have the humility to admit you can't predict market size and instead back the visionary founder.