title: The "Optimize code" checkbox in Visual Studio. What exactly does it do?
body: <p>The Build tab of the Project Properties in Visual Studio 2005/2008 contains the "Optimize code".</p>
  
  <p>The documentation states that it "... enables or disables optimizations performed by the compiler to make your output file smaller, faster, and more efficient."</p>
  
  <ol>
  <li>My question is why should I NOT have it on?  </li>
  <li>Why is it not on by default?  </li>
  <li>What does it actually do?  </li>
  </ol>