(CNN) -- Skim through the photos on Flickr or Photobucket, and you'll find pictures of cats pawing at living-room sofas, children playing in backyards and mothers gardening at home. Dig a little deeper, and you can unearth the exact locations of many of those homes, embedded in data within the pictures. Images often contain a bundle of information and various traces left by digital cameras or photo manipulation software. This data, called Exchangeable Image File Format (EXIF), is a key tool for many professionals. It can detail whether the photographer used a flash, which digital effects were applied to a picture and when the photo was taken.
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Images can contain the precise GPS coordinates for where a photo was taken
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Pictures on Flickr, Photobucket and Picasa Web Albums can contain location data
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Other services, like Facebook, TwitPic and Yfrog, strip that data
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Digital photo experts express concerns over privacy implications
Judging by the abundance of pictures in @placeholder's database that include geolocation data in the EXIF, some smartphone owners aren't thinking twice about opting into their devices' GPS feature.
(@placeholder says it strips the EXIF data from all photos to protect its users' privacy.)