This time, the things are Fitbits and other personal data trackers. Fitbits don't just track your running, they report it. It's data you can use personally to reach new fitness goals. And your personal information is removed, but the aggregated data is published online.
Which means anyone can see it.
This is a screenshot of Kandahar from the Strava website. The running track stands out of the background in what the company calls a heat map.
Now Kandahar might not be revealing much, because everyone knows the U.S. is there. But what about a lot of Fitbit jogging activity near a suspected CIA compound in Somalia? Or the guys that are monitoring all their daily activity and wear their Fitbit on patrols or while working outside their bases?
It's clearly detailed enough to make it usable intelligence for an enemy.
Here's the Washington Post article.