Certainly I know some people of U of I who worked on it, but Hadoop isn't developed for a Yahoo user. It is used mainly for serving ads and doing market analysis. A normal Yahoo user reads their mail and the sports page. Google makes its bread by facilitating advertizements on other peoples websites - it provides these kinds of technologies to other people. How they put up advertizements is their choice. Google's clients are responsible for content. Yahoo is more about providing media, they happen to make revenue with their own internal advertizements.

Google's primarily goal isn't to own every computer screen, they just hope that their ads make it to every screen. Yahoo's goal is to fill every screen. For Yahoo buying screen space is a end in itself.