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Fortresses
Hard to copy, hard to dislodge, and they grow without growing costs. All three at once is rare.
3 teardowns · $1M–$10MEvery teardownFortressesEasy to copy. Won anyway.Built on rented landNumbers straight from a filingDoesn't scale. On purpose.Still here after 15 yearsOne-time money
BiggerPockets
Community
Real estate's town square — a free forum, 3M+ members.
$7M
Estimate · 2016 rev · last public
⚠ Need cyclical
under 1% pay
under 1% pay
★ The edge: Dorkin kept the forum free for years before charging — trust and UGC compounded into a moat rivals can't buy.
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Shodan
Data
Google indexes web pages. Shodan indexes devices.
3M+
Stated · registered users
Key-person lean; Censys cloned it with VC.
★ The edge: A 15-year, continuously-crawled index of every service on the public internet — a dataset newcomers can't back-fill.
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World Anvil
SaaS
Build your fictional world — a wiki for writers & GMs.
3M+
Stated · users
⚠ Need niche
small TAM · free-heavy
small TAM · free-heavy
★ The edge: anyone can clone a wiki — the lock-in is years of your interlinked lore living inside it, plus a 3M community.
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