Larry at My Vast Right Wing Conspiracy has found an excellent example of what happens when the media chooses what information should be classified, and which should not:

You may recall that in April 1983, some 60 people were killed in a bomb attack on the U.S. embassy in Beirut. At the time, there was coded radio traffic between Syria, where the operation was being run, and Iran, which was supporting it. Alas, one television network and a newspaper columnist reported that the U.S. government had intercepted the traffic. Shortly thereafter the traffic ceased. This undermined efforts to capture the terrorist leaders and eliminated a source of information about future attacks. Five months later, apparently the same terrorists struck again at the Marine barracks in Beirut; 241 servicemen were killed.

23 years later and our press has yet to learn this simple fact. You fail to safeguard classified information and people die. But at least they get their pulitzers.