Potent dangers to the growth and health of the Internet involve a human element and require understanding of Internet economic issues. The Internet as an economy currently includes about 50,000 organizations that interconnect their communication infrastructures to provide the global Internet service to more than 3 billion users. The interconnection structure and economic relationships between the organizations have deep implications for performance and security, e.g., for traffic routing through the Internet and resilience of the Internet service to failures and attacks. Our research in Internet economics studies individual interests of Internet players, tensions between these interests, incentives for cooperation, and mechanisms for improving the social welfare.