title: Why does BigTable have column families?
body: <p>Why is BigTable structured as a two-level hierarchy of "family:qualifier"? Specifically, why is this enforced rather than just having columns and, say, recommending that users name their qualifiers "vertical:column"? </p>
  
  <p>I am interested in whether or not enforcing this enables some engineering optimizations or if this is strictly a design thing.</p>