1. Computer systems are inherently flawed and too unreliable for critical or vital tasks. They cannot be designed without the ever-present threat of life-endangering malfunctions because their very complexity makes thorough testing for errors impossible. The way they are built means that they are prone to total catastrophic failure, rather than partial failure. As they become more complex, so the level of the catastrophe increases. For these reasons they are dangerous when used in sensitive areas such as intensive care wards, the nuclear industry, air traffic control and early warning and strike command systems. Checking a typical power station's computer program to ensure it is error free under all conditions would take software testers literally trillions of years.
2. If builders built buildings the way programmers write programs, then the first woodpecker to come along would destroy civilization.