Just a reminder that digital photos often include data about where they were taken, so if you post photos online, other people may be able to find out things like your home address.
Background and more info:
Most smartphones, and some digital cameras, contain GPS units. When you take a photo with such a device, the location where the photo was taken gets automatically attached to the photo. This attaching of location data to an image is known as geotagging.
Geotagging is great for all sorts of purposes; it can be very handy to be able to map your own photos.
But that location info remains attached to the photo when you email the photo to someone, or when you post it online. It's attached in a way that's invisible to the naked eye (so there's no reminder to you that it's there), but that's trivially easy for anyone to view if they want to.
Presumably you don't care if there's a geotag attached to, say, your photo of the Grand Canyon, because if someone looks at that geotag, all they find out is the location of the Grand Canyon. But if you take a photo at home (with a device that uses GPS), that photo contains the latitude and longitude of your home, which can easily be translated to your home address. That may be fine with you or it may not, but it's a good thing to keep in mind either way.
There's a reasonably balanced ABC News video describing the issue and giving some examples. It gets a little alarmist in places, but overall pretty good. (3 min) (via Holly H.)
That report mentions I Can Stalk U, a site that looks for pictures posted to Twitter and figures out where they were taken. Worth a look if you're interested in this stuff.
Shifting away from geotagged photos toward the more general issue of sharing your location online:
As the news report mentions, there are plenty of contexts in which you want your location to be known. For example, they mention Facebook Places—but they apparently didn't research it, because they express a hope that it can be turned off, whereas in reality that feature is entirely manual; Facebook doesn't know where you are unless you explicitly check in. Same with services like Foursquare.
I occasionally check in to Facebook Places, but only when I'm not at home. (It wouldn't be too hard for someone to find my home address online, but I try not to advertise it.) (Of course, some argue that checking in when away from home lets potential burglars know that you're not home.)
Another service I like for location-sharing is Google Latitude. You can run it as an app on your iPhone or Android phone, and it will constantly track where you are; you can then share that location with friends. (Yes, you can turn it off.) I would personally be reluctant to post that information publicly (just on general privacy-paranoia principles), but I like sharing with a small circle of friends who also use Latitude.
(Actual friends of mine who use Latitude are welcome to invite me to connect to them, but I don't promise to accept invitations, and unlike on Facebook, I will definitely not accept invitations from people I don't know.)
(Wrote this entry in late January, didn't get around to posting it until March.)