My camera does not have a GPS receiver to automatically generate location information; however, GeoSetter provides an easy way to add this information to photos. GeoSetter works particularly well if I know the address where a photograph was taken. It adds this information directly to the image metadata, so it will always be associated with the image.
At this time, I do not have a specific purpose for adding GPS information; however, I believe it will be useful locating photos in the future, as I take more and more photos.
Some newer cameras, such as the Nikon P6000, and cell phones add this information automatically, and I certainly expect that my next camera will have this feature. I also hope my next camera will use this information to automatically set the date and time, so that this information is also correct.