I can't find it right now, but I know someone gave a talk on Apollo, which is how Amazon does deployments.
I did find 'flippers' from Flickr[1] which sounds like a very similar "keep it all in master and turn stuff on and off" methodology.
[1] http://code.flickr.com/blog/2009/12/02/flipping-out/
http://news.ycombinator.com/item?id=2971521
I can't find it right now, but I know someone gave a talk on Apollo, which is how Amazon does deployments.