What do you do when you can use the Internet to data-mine a collection of billions of photos?
The FlickrTrends application takes advantage first of the API (application programming interface) at Yahoo's photo-sharing site, Flickr, which can show how many photos have been tagged with a particular word over a period of time. Second, it uses Google App Engine to present the relative popularity of two tags in chart form to show what's waxing and waning.
Flickr employee Kellan Elliott-McCrea wrote the application, deriving it from another by Derek Gottfrid that compares how often terms are mentioned in The New York Times. The idea came to broader light on Wednesday with a posting on the Flickr Code blog.