title: Why would one want to use AttributeUsage AllowMultiple when creating attributes?
body: <p>According to a book I'm reading, the <code>AllowMultiple</code> public property of <code>AttributeUsage</code> specifies:</p>
  
  <blockquote>
    <p>...whether the target can have multiple instances of the attribute applied to it.</p>
  </blockquote>
  
  <p>Why would I want/not want to use this?</p>