I knew that this solution would work because computers are great at doing exactly what they’re told. Unfortunately it turned out that many times we humans who program them are not so good at telling computers exactly the right thing to do, and that is a major source of bugs. When two computers are supposed to be doing the same thing, but disagree because of a bug, well, that’s a problem. – Patrick Wyatt

http://www.codeofhonor.com/blog/the-making-of-warcraft-part-3