title: What is a "feature flag"?
body: <p><a href="http://highscalability.com/" rel="noreferrer">High Scalability</a> mentions feature flags here:</p>
  
  <p><em><a href="http://www.iheavy.com/2011/08/26/5-things-are-toxic-to-scalability/" rel="noreferrer">5 things toxic to scalability</a></em>, <em>"5. Lack of Feature Flags"</em></p>
  
  <p>What exactly are feature flags?</p>