On a Philosophy Forum someone asked, "What makes a good friend?"
  along with a quote, "A friend for all is a friend for none".* So
  here's my response: A good friend? It's a formula involving your
  tolerance of the ways they piss you off. Bad friend is one who
  goes over a particular line. Good friend will still piss you
  off, but it's in ways within your tolerance zone. You can be a
  friend to all but of differing degrees. Thoughts?