The irony dripping off the Petraeus/Broadwell/Kelley affair is rich and bitter. Consider: The man who brought the disastrous counterinsurgency mentality back from Vietnam into the current debacle in Afghanistan moved over to the CIA, thus assuming executive responsibility for the civilian-killing drone program that is the jihadists' single best recruiting tool. The Afghanistan surge, which Petraeus advocated, was and is a colossal waste of blood and treasure, whose net effect is to leave the Taliban stronger. That alone should have doomed him, let alone helping direct a remote-control murder program that has veered from imperial arrogance to war crimes (secondary strikes on rescuers and funerals. Go on, look it up, I'll wait.).
But what brings him down is...a perfectly legal extramarital affair. Not with a Russian spy, mind you, but an American in the military establishment who could not be more loyal to Petraeus and all he stands for.
What's really rich is the method of his destruction. A prime mover of the invasive American surveillance state (though, supposedly, uninvolved with domestic surveillance) has his email traffic peeped by the FBI...why? Suspicion of a crime? National security issues? Terrorism? No, an FBI agent had a thing for yet another (married) woman, and used his police powers to pry into two citizen's private lives in order to please her.
The whole sordid thing is a metaphor for how low we've sunk as a nation of laws and liberties.