I teach people how to use cryptography. A lot of it is step-by-step software walkthroughs. Behavioral changes are harder.

On a whim I opened Instagram this evening and searched for #tree. I've no hard data whatsoever, but I guessed two things: 1) Many people's Instagram feeds are public. 2) A non-negligible percentage of people's photos of Christmas trees are the ones in their home (and not public ones like the Rockefeller Center's). The un-blurred photo on the right, with four people in it, was tagged #tree.

Turns out, yeah -- some people are tagging photos with #tree that look like they could be taken in a living room, and some of those photos look like they could be in suburban areas. (You can see a user's geotagged photos by clicking on the pin in their profile page.)

From here, you get a map of all that user's geotagged photos. From there, it's just a question of pinching and zooming in to street level. Maybe this data's only useful when combined with other data, but even so, it's a lot of data in and of itself.

It doesn't help that Instagram offers you a handy pop-up when you first load the app, asking for geotagging permission while apparently not giving you a warning that this means that if you take a geotagged picture at home on a public Instagram account, other users can see the location down to street level.

Instagram users who choose geotag photos keep where the photo was taken in mind (and, to not geotag a photo, keep "Add to Photo Map" turned off), but I think some of the onus should be on Instagram to alert you to this pitfall.