Yahoo's support of Hadoop extends back to 2004.  Yahoo! started with a 20-node cluster in March 2006, increased the size to 200 nodes a month later, and has since continued to invest in grid computing. In Sept. 2008, Yahoo! constructed the largest Hadoop cluster to date with 4000 nodes.

Yahoo! has a history of supporting open source software including Apache, PHP, MySQL, Zimbra, and most recently, YUI.  In contributing to the Hadoop project, Yahoo! hopes to make Hadoop's "scalable, economical, efficient, and reliable" feature-set available to an ever-expanding community of users