Yahoo! needs something strong and innovative to come out of the shadow of Google, and recently Microsoft. It has taken the route of letting others build on its search results, and I think this is a good approach. Yahoo! is offering Open Search Platform, geekily called SearchMonkey, which will let third parties modify the search results, except the order of results, to improve the experience.
Users can inject more information into the search results using the Open Search API. This can not only improve quality of the information, but it also offers an opportunity to improve the discoverability of content. If this can better what Google offers, Open Search Platform will do a whole lot of good to Yahoo.
Coupling this with the Open Search Platform, users can build a search engine which looks deeper into the Web. I think this is good news, and it is good that it is coming from Yahoo, which deserves more credit and visibility.