title: Knockout issue with prototypical inheritance
body: <p>I have an issue with Knockout where I prototype a user object where the observable properties of my object seem to be overwritten by the last occurrence.</p>
  
  <p>Therefore I cannot use the same object more than once otherwise it will be overwritten.</p>
  
  <p>Although this is hard to explain, see my fiddle.</p>
  
  <p><a href="http://jsfiddle.net/RSEcj/1/" rel="nofollow">http://jsfiddle.net/RSEcj/1/</a></p>
  
  <p>What am I doing wrong? (or is this a bug in Knockout?) How can I fix the problem.</p>