In the latest sign of the rapidly shifting forces on the Web, Yahoo Inc. acknowledged it faces increased competition for online advertising dollars from both new and established rivals.
For several years, Yahoo, Google Inc. and a few other large sites have reaped the lion’s share of U.S. online-ad spending without significant challenges from upstarts. Now, the explosive growth of new players in areas such as online video and social networking is drawing the attention of advertisers, potentially giving some of the established sites a run for their money.
The development is a further sign of fast changes to the Web landscape and the perils facing any large Internet companies that don’t successfully ride successive new waves of consumer trends.
