If CIA Director Porter Goss resigned because of a sex scandal, it will rock Washington, affect the midterm elections and give us all a lot to chew on for weeks or months. But long term, it will also indicate something of critical importance in understanding why President Bush will be viewed by history as a failed president: Apparently the only way to lose your job in the Bush Administration is by being disloyal (Paul O'Neill, Larry Lindsay) or by being a sleaze. Being incompetent is not a problem.
It's like the Watergate scandal, where after the "smoking gun" tape was revealed and Richard Nixon had to resign, all future scandals were only deemed serious if they featured a smoking gun. We don't know the details yet on Goss. Maybe he's innocent. But if he's not, the Goss firing may similarly raise the bar on what it takes to be relieved of one's duties. Anything short of being caught with hookers and you get to stay on.
In researching my book on Franklin Roosevelt, one of his great secrets of success became clear. Where Bush puts loyalty ahead of performance, FDR almost always put performance ahead of loyalty. He didn't go around canning people, but if you were not doing the job, you were quickly frozen out. He was reluctant to fire over scandal. For instance, when Undersecretary of State Sumner Welles was caught propositioning a railroad porter, Roosevelt was furious at the government official who exposed him. But his patience for anyone who wasn't good at his job was extremely thin, then non-existent.
This sounds simple but it's a rule of thumb for all presidents and all leaders: If you only fire people who embarrass you, you will fail.