Flickr Trends: Compare popularity of cats and dogs, good and evil

What do you do when you can use the Internet to mine a collection of billions of photos?

Find out whether cats are more popular than dogs, of course. Or whether good outdoes evil. Or any other comparison that takes your fancy.

The Flickr Trends application takes advantage of the API (application programming interface) at Yahoo's photo-sharing site, Flickr, that can show how many photos have been tagged with a particular word over a period of time. It also 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.

By showing usage over time, the application shows come seasonal curiosities. For example, it appears that people consider summer and winter each to be longer than spring and autumn.