title: When should I guard against null?
body: <p>When should I guard against <code>null</code> arguments? Ideally, I would guard against <code>null</code> everywhere, but that gets very bloated and tedious. I also note that people aren't putting guards in things like <code>AsyncCallback</code>s.</p>
  
  <p>To keep from annoying other people with lots of unidiomatic code, is there any accepted standard as to where I should guard against <code>null</code>?</p>
  
  <p>Thanks.</p>