An FBI agent told superiors that his friend Jill Kelly was subjected to e-mail harassment. The subsequent investigation did not uncover a crime, but it ultimately forced David Petraeus to resign as Director of the CIA. The incident is being cited as evidence that technology and laws passed since September 11 demonstrate how vulnerable innocent Americans are to invasions of privacy by government agencies, turning the US into a "surveillance state." Why don't constitutional protections apply to e-mail? What's the role of Google, Facebook and the Cloud?