title: Are duplicates useful in data sets?
body: <p>I downloaded <a href="https://archive.ics.uci.edu/ml/datasets/Skin+Segmentation" rel="nofollow">Skin Segmentation Data Set</a> and found that it contains a lot of duplicates.<br>
  For example, this row <code>0 128 0 2</code> encountered 199 times.</p>
  
  <p>Please, supply a few examples when duplicates is good and when is evil.</p>