The Fed was created with the "official" purpose on fighting inflation and managing the business cycle. However, since its inception it has proven totally incompetent of doing either of them. The Fed is the main source of inflation, and its actions result in a more violent business cycle because it denies the market a real recovery.
I'd dare to say that we've managed to avoid something truly catastrophic thus far... such as mass homelessness and starvation.
Who's to say what would've happened without it?
I've heard differing theories for both sides... some saying the Fed tends to retard recovery... while others contend that the Fed makes the downtimes less awful, so the extended recovery is worth it.
I think something is necessary to control the money supply... something central anyway... don't want states and individual banks to be issuing their own notes backed up by who knows what... like the value of land or the price of cotton.