Modern societies are risk societies. Together with the formidable development of complex technologies (chemical industry, energy production, mass transportation, etc), new hazards have emerged. Sharing danger is the hallmark of modernity, as large industrial accidents can now have countrywide, or even, worldwide consequences. The Chernobyl explosion for example, has smeared large European surfaces with radioactive materials, across borders and nations, without any regard for who was responsible and who was the victim. Complex technologies should therefore be managed with great foresightness, particularly focusing on preventive management. A sound understanding of the (minor) role of human errors of operators and the (major) role of process design is a pre-requisite for appropriate management. This also applies to the complex business of radiotherapy, as the same organisational principles apply than in the heavy industry: restrict the role of operators, expect their mistakes, design in a mistake-proof way, accept the burden of preventive maintenances, supervise maintenance carefully and, above all, invest in safety.