I found this via the etsy “code as craft” blog: http://velocityconference.blip.tv/file/2284377/

My big takeaway is validation of something I have always done – code configuration by user/bucket/site is a “good thing”. It’s so much easier to roll out changes to a select population and deal with changes that way. Something I like to do using django groups. It is a sort of a/b testing, but just a little different. Very useful.