Well I know this may be interpreted as out of subject (the thread was split) but this comes as an answer to some (supposedly) experts here and as an effort to make some people see that Murphy's Law should always be considered everywhere, anytime.
Some excerpts from an study dealing with problems with a machine called "Therac25". Please someone point out whether or not its a trustworthy source:
Despite what can be learned from such investigations, fears of potential liability or loss of business make it difficult to find out the details behind serious engineering mistakes. (Underline is mine)
Most accidents are system accidents; that is, they stem from complex interactions between various components and activities. To attribute a single cause to an accident is usually a serious mistake. In this article, we hope to demonstrate the complex nature of accidents and the need to investigate all aspects of system development and operation to understand what has happened and to prevent future accidents. (underline is mine)
The paper can be obtained @
http://courses.cs.vt.edu/~cs3604/lib.../Therac_1.html