Why do we have a Fed? (fg)

This question was recently posed by John Steward, precisely the words were: "Why do we have a Fed? Why do we have someone adjusting the rates if we’re a free-market society?" Mr. Greenspan himself had the plessure to answer this fundamental question. Here you can find the video on comedy central (highly receommended). Well, Mankiw advices everyone to think about this question and as soon as somebody might find an answer, he should publisch in the AER. Amv, you might offer a non-positiv answer, don't you?