This is why you should be very careful with photos taken on your iPhone and other cameras with built-in GPS.<br/><br/>
If you allow the iPhone to use your location when taking pictures, the GPS coordinates are stored in the file, using the <a href = "http://en.wikipedia.org/wiki/Exchangeable_image_file_format">EXIF</a> specification.<br/><br/>
I've used three images I've taken on my iPhone, pulled the EXIF data from the file, and used Google Maps to show the location (green arrow) of where the picture was taken.<br/><br/>
Due to some inaccuracies in the iPhone GPS, the actual location is off by 50-100 feet. However, this information could still be used in a way that you may not be comfortable with; do you really want a stranger knowing where your house is because you took a picture in your house.
Most photo upload services either strip the information from the file, or give you the option to include it or not.<br/><br/>
I've done some testing with pictures uploaded to Facebook, and it looks like Facebook strips out the GPS information. Flickr gives you an option to strip it out. However, emailing pictures does not.  
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