Humans kill 73 million sharks every year, nearly all for consumption, mainly in shark fin soup. The fins are cut off and the bodies dumped overboard, a barbaric practice known as finning. Commercial fishermen are taking more and more sharks for their meat as well.
Nearly a third of shark species in the open oceans are threatened with extinction. Losing these top predators creates a cascading imbalance. The species whose numbers the sharks once controlled begin to explode; they then wipe out smaller fish, some of which humans depend on for food. Water quality suffers. Healthy oceans require sharks, and without healthy oceans, healthy fisheries are impossible.
From the NYT, July 28, 2009.