Clarification on Yahoo! and it's use of PHP. They used to be a pretty heavy PHP shop, but there has been a consistent effort underneath to move away from PHP towards Javascript, more notably the new version of Flickr being a Node.js application. Eventually they'll stop using PHP and basically have from what I have heard. Nothing new gets written in PHP at Yahoo!
I noticed Flickr is on the list as well being incorrectly listed as a PHP site, it's Node.js now... The Flickr engineering team even wrote a blog post about it and I have spoken with Yahoo! developers who worked on the redevelopment effort.