It came to light at the end of June that Spotify is switching their 5,000+ back-end servers to Ubuntu from Debian. Why? The reasons expressed by Spotify's Noa Resare come down to Ubuntu having the advantages of a predictable release cycle and long-term support (LTS) releases that extend beyond Debian's support window. While Spotify's decision was made months ago, since then the Debian developers decided to extend Debian 6 as a LTS release. Debian 6 "Squeeze" is now being maintained until February 2016 and Debian developers also hope to make Debian 7 "Wheezy" and Debian 8 "Jessie" long-term support releases too, due to organizations interested in the longer support. The Debian LTS plans though still don't do anything to help Spotify's other concern about predictable releases with Ubuntu sticking to a six month release cadence and LTS releases every two years.
The information about Spotify abandoning Debian for Ubuntu on their thousands of servers was shared via the Debian mailing list.