Because the platform is open it gives all Web site owners -- big or small -- an opportunity to present more useful information on the Yahoo! Search page as compared to what is presented on other search engines. Site owners will be able to provide all types of additional information about their site directly to Yahoo! Search. So instead of a simple title, abstract and URL, for the first time users will see rich results that incorporate the massive amount of data buried in websites -- ratings and reviews, images, deep links, and all kinds of other useful data -- directly on the Yahoo! Search results page.
via: Yahoo Wants to Redefine SERPs, Adapts “Open” Approach
Related: Viewing Unpersonalized Google Search Results - Yahoo Tops Customer Satisfaction Results? - Improved Web Search (Jan 2006) - Improve Google