There's a weird thing with politics and infidelity... no one cares about movie stars, business men, lawyers, doctors, teachers, cops, firemen, etc having affairs. But somehow, when a politician gets caught cheating it is some big deal.
Politicians come from the general public. They have the same incidence of vice as the rest of us.
Is there some big surprise that a guy who spent years away from his family in a war zone and now works long, demanding hours at the office had a relationship with the cute chick following him around? Doesn't make it right, but I can see how it happened.
Petreaus should have known he needed to J Edgar it up.