"If a friend is someone who laughs at our stories, then a good friend is one who enjoys them even the second time around."
This New York Times article talks about studies that show people often remember where they heard something but not to whom they told it. Hence the retelling. Hence the need for good friends.
Apparently I'm not the only one who can't remember to whom I told a story. I'm so relieved. Also, note that a good friend will enjoy my stories a second time around... hint hint.