In web3, the situation is different.  New marketplaces can aggregate all existing NFTs. New social networks can surface all on-chain activities regardless of whether users ever signed up. How can a moat develop?  A potential answer is tokens.

Defensibility in web2 comes from proprietary data network effects. Each application is a walled garden, and a bigger user base translates into more utility vs. competitors.  The social network with most data, content, users, etc. is more valuable.