The MIT Technology Review has an article about the rise of "geotagged" digital photos. Cellphones and digital cameras increasingly have built-in GPS (Global Positioning System) capabilities, allowing users to easily add metadata about exactly where a photo was taken. Why? If a picture is worth a thousand words, a picture with geotagging can add a few hundred more. Uses mentioned in the article: naturalists can map their bird sightings or chart out seal populations; archaeologists can mark where they unearth artifacts; travelers can add a new dimension by adding maps to slideshows.
The geotagged photos are showing up online, of course - one site, Jelbert, is trying to create a photographic map of every street in the world.