A product that gets more useful as more people use it. They start in one small market and rarely across a whole one.
Name the two sides, say which one pays and why, and describe exactly how one side's growth helps the other.
Marketplace and platform pitches, product strategy questions, and the marketplace model.
From Platform Revolution · Geoffrey Parker, Marshall Van Alstyne and Sangeet Paul Choudary
Ask how a business escapes competition before asking how large its market is.
Venture and growth interviews, any moat discussion, and any pitch that leads with market size.
From Zero to One · Peter Thiel and Blake Masters
Judge a network by whether its first small market is dense and self-sustaining, not by the size of the market it aims at.
Early-stage diligence, growth strategy questions, and any marketplace that reports total users rather than density.
From The Cold Start Problem · Andrew Chen