Code: Flickr Developer Blog » Flipping Out
http://code.flickr.com/blog/2009/12/02/flipping-out
Flickr is somewhat unique in that it uses a code repository with no branches; everything is checked into head, and head is pushed to production several times a day. This works well for bug fixes that we want to go out immediately, but presents a problem when we’re working on a new feature that takes several months to complete. How do we solve that problem? With flags and flippers!