You may be awesome at keeping the lid tight on your online data. Like, “Leader of the CIA” tight. But how about your friends?

The collapse of the impressive career of CIA Director David H. Petraeus was triggered when a woman with whom he was having an affair sent threatening e-mails to another woman close to him, according to three senior law enforcement officials with know­ledge of the episode.

The recipient of the e-mails was so frightened that she went to the FBI for protection and help tracking down the sender, according to the officials. The FBI investigation traced the threats to Paula Broadwell, a former military officer and a Petraeus biographer, and uncovered explicit e-mails between Broadwell and Petraeus, the officials said.

When you share data, you share data with everyone that your partner ever shared data with…

BTW, an email counts as “data”. Even if the accounts are anonymous (as Broadwell’s seems to have been). Service providers are being asked to give it up more and more all the time. And they frequently comply.

Via Sari Horowitz and Greg Miller at The Washington Post. For more technical info, click through Ars Technica’s coverage.