EXCERPTS:<p>DoubleClick Ad Exchange, will greatly simplify the process of buying and selling display advertising, allowing many more publishers and advertisers to benefit from it.<p>But both in display advertising and in advertising exchanges, Google finds itself in the unfamiliar role of underdog. As one of the Web’s biggest publishers, and a seller of ads on a network of top sites like eBay and hundreds of newspapers, Yahoo is the king of the display advertising business.<p>The new system will automatically allow hundreds of thousands of advertisers and publishers who now use Google’s AdWords and AdSense systems to run their ads and ad space through the exchange.