Like so many other great ideas and technologies for the Internet, Flickr emerged from a soup of game thinking. Nice interview with JJG:

adaptive path » an interview with ludicorp’s eric costello

JJG: How much of The Game Neverending would you say is still present in Flickr in its current state?
EC: I think the spirit of it is there, definitely. Someone once described Flickr as “massively multiplayer online photo sharing.” I think that’s a good description. There’s kind of a feeling of exploration within Flickr. It feels like a world where you can move around and find wonderful things – the wonderful things being the great photographs that people upload.
And because it’s got the social network aspect of it, you can kind of build neighborhoods within Flickr. The page in Flickr that shows you all the photos from your friends and family is very much a space like you might find in a game. It’s a place where you go and interact with the people you know.