Yahoo has been on a mad dash to go ultra open with all of their properties. They have been talking for the last couple of months, around the time of the MS take over bid. They have had APIs(application program interface basically tools to give you access to their programs), available for products like Upcoming, Flickr, Fire Eagle, Mobile, etc... Recently they have opened up their Search APIs with Search Monkey and BOSS. This new batch of programming tools will give you access with their Social Directory, Contacts, User Status and Updates and also YQL. Unfortunately we only get to read about what these new tools can do for us. Hopefully they will release the code soon but for now we can only read the documentation.
We will have to see if opening up all of their properties will draw the developers in to program on their platform and add value to their properties like it did for the likes of Facebook, the iPhone, Meebo, and many of the other sites and tools that have opened up.