Why can my agent not tell a real service provider from a Sybil?

As AI agents begin hiring other agents for tasks, they shop in open permissionless marketplaces where creating a new identity costs nearly nothing. Adversaries register dozens of fake providers, seed them with fabricated reviews, and consistently win selection from reputation-weighted routing algorithms. A June 2026 empirical study of deployed ERC-8004 agent ecosystems found Sybil accounts representing 73.5% of reviewers on Ethereum and 90.6% on Base. The buying agent has no way to distinguish these from legitimate providers before funds are committed. No production payment authorization system today enforces Sybil-resistant identity checks before an agent pays a counterparty it found in an open registry.