title: When to use form vs model validation?
body: <p>Just curious. What is the best practice for when to use form vs model validation?
  From what I understand currently, form validation should be used for:</p>
  
  <ul>
  <li>AJAX / HTTP requests params</li>
  <li>Forms that do not correlate to a model?</li>
  </ul>
  
  <p>Another question is: I have a HTML form that roughly correlates to a model instance, do I use a ModelForm for it?</p>