title: Why is "copy and paste" of code dangerous?
body: <p>Sometimes, my boss will complain to us:</p>
  <blockquote>
  <p>Why do we need such a long time to implement a feature?</p>
  <p>Actually, the feature has been implemented in another application before, you just need to copy and paste codes from there. The cost should be low.</p>
  </blockquote>
  <p>It's really a hard question, because copy and paste codes is not such a simple thing in my point of view.</p>
  <p>Do you have any good reasons to explain this to your non-technical boss?</p>