IARPA, the research body of the intelligence community, wants to know where you took your vacation:
"In an announcement for its new “Finder” program, the agency says that it is looking for ways to geolocate (a fancy word for “locate” that implies having coordinates for a place) images by extracting data from the images themselves and using this to make guesses about where they were taken.
More and more digital cameras today don’t just take pictures but also capture what is called metadata — often referred to as data about data — that can include everything from when the picture was taken to what kind of camera was used to where the it was taken. This metadata, often stored in a format called EXIF, can be used by different programs to understand different aspects of the image — and also by intelligence analysts to understand different aspects of the user who took it, and the people who are in it. Like who they are, what they are doing, and where and when they did it."
Most of the metadata can be read already by anyone. Don't want to share this data with the world? Process your images through a photo-editing software before posting them online.