Ethereum co-founder Vitalik Buterin has raised concerns about the development of critical systems in healthcare, finance, and governance, warning against their construction in closed, centralized ways. He stresses the importance of open-source and verifiable models to ensure trust and security. Buterin highlights the risks associated with proprietary health tracking systems, such as data monopolies and potential blackmail, and calls for greater openness to mitigate these dangers. He also warns that closed systems in finance and voting could conceal flaws and manipulation, advocating for a focus on privacy and security to build reliable technology.