Peer-to-peer (P2P) exchanges of goods and services already exist, such as Facebook Marketplace, which acts as an intermediary without charging commissions. However, this has also made it a breeding ground for scammers precisely because the transaction is directly between individuals and the platform doesn't manage anything. How can fraud be prevented in blockchain, especially in e-commerce? I believe there are many aspects that theory cannot foresee or resolve without the need for trusted intermediaries.