Enjoy that family birthday party on the weekend? Use your new GPS-equipped phone to take a few piccies? Upload them for family and friends? Excellent. Maybe a stalker just got what they needed to track your every move. Or your kids. Having GPS navigation in your phone is handy. Saves all that strenuous turning of street directory pages and, you know, thinking. It makes it easier to sort your photos too by geotagging every image. Even without GPS, the software that organises your photos taken with any camera can be used to add the location later, along with event details and keywords. With Apple’s iPhoto software now having face recognition, your computer can even identify who’s in each picture and create nifty maps of what you did on the weekend. "Metadata”, that's called: data (such as date, time, place and keywords) about some other data (the photo itself). Metadata is great for anal retentive photographers. But once you’ve added it to a photo, it tends to stick around – because it’s recorded within the photo file itself using the EXIF standard. Modern photo-editing programs keep that metadata intact. That’s deliberate, because professional photographers want to preserve their copyright notice and other identifying data. But often that metadata stays with your photos when they’re uploaded to the web, and that’s where the risks to privacy start. Maybe you don’t mind putting family photos online, but if they’re geotagged anyone can copy the GPS coordinates, paste them into Google Maps Street View and bingo! There's a photo of your house and they can confirm… yes! It’s the one with the green fence. Maybe you didn’t mention your children’s names, but the keywords “Joshua” and “Emily” are right there in the metadata. Maybe you didn’t say which school they go to, but you tagged the photos “Orange Grove”. Maybe you were careful, but what about all the other guests at your party? Upload a week of photos from family events, a work function, that funny-looking dog you saw at the railway station, that delicious steak at the pub – all geotagged and timestamped -- and a stranger can soon figure out exactly where you live, where you work, how and when you get there, and where you relax and let your guard down. Did you just tweet that the train’s been cancelled again? “Hello, Emily? Sarah… sorry, your mum’s running late. I’m her friend Brian. I work with her at the bank. Sorry I missed your birthday party last weekend, but I’ve got a present here for you...” As it happens, Facebook and some other sites delete the metadata from the photos you upload. The threat from paedophiles online is vastly over-stated. But many other sites, including Flickr, don’t delete those keywords. It’s easy to forget you turned on your phone’s GPS. Even if you’ve restricted your Facebook photos to people in your network, the “Australia” network contains three million people. Bad people do exist. By all means choose not to be paranoid. But maybe you want to make it an informed choice.