The document discusses computer reliability and the issues that can cause computers to be unreliable. It notes that computers are subject to hardware failures, software bugs, and communication failures. Specific examples provided include the Therac-25 radiation therapy machine that caused overdoses due to system malfunctions, and the Y2K bug caused by storing years with only two digits. The document also discusses the concepts of hardware reliability, software reliability, and data reliability. It emphasizes that computer professionals have a responsibility to provide fault-tolerant systems, while individuals also bear responsibility to properly use computer systems.