Yahoo tells users they want to track everyone and will not recognize "Do Not Track Me" requests.

Yahoo! has been working with our partners in the Internet industry to come up with a standard that allows users to opt out of certain website analytics and ad targeting. In principle, we support “Do Not Track” (DNT). Unfortunately, because discussions have not yet resulted in a final standard for how to implement DNT, the current DNT signal can easily be abused. Recently, Microsoft unilaterally decided to turn on DNT in Internet Explorer 10 by default, rather than at users’ direction. In our view, this degrades the experience for the majority of users and makes it hard to deliver on our value proposition to them. It basically means that the DNT signal from IE10 doesn’t express user intent.

Ultimately, we believe that DNT must map to user intent — not to the intent of one browser creator, plug-in writer, or third-party software service. Therefore, although Yahoo! will continue to offer Ad Interest Manager and other tools, we will not recognize IE10’s default DNT signal on Yahoo! properties at this time.
http://www.ypolicyblog.com/policyblog/2012/10/26/dnt/