SAN DIEGO (TheStreet) -- Social networks are attracting more digital advertising dollars at the expense of search engines, according to the latest estimates from digital analytics firm eMarketer.

In 2015, eMarketer forecasts that Facebook's (FB) - Get Report digital display ad revenue will total $6.82 billion, around one-quarter of the total U.S. market. Its share will continue to edge upward and hit 26.9% by 2017, while Google's (GOOG) - Get Report (GOOGL) - Get Report share of the U.S. digital display ad market will slip from 13% this year to 11.1% in 2017. 

Twitter (TWTR) - Get Report, meanwhile, will take a 5% share this year, surpassing Yahoo! (YHOO) , which will take home a 4.6% share in 2014. By 2017, Twitter will own a 6.8% share of the digital display ad market in the U.S., while Yahoo will possess just a 3.5% share.

"Many brand marketers are moving direct response ad dollars from search to display, and social networks are the main beneficiary of this trend," eMarketer senior forecasting analyst Martin Utreras said. "Because consumers share personal information and interests openly on social networks, brands are shifting budgets to reach them there, especially as sites like Facebook and Twitter become more sophisticated in collecting consumer data for more effective ad targeting."

The divergent path of social networks and search engines is also correlated with a flip in advertisers' growing preference for mobile, where social networks have the edge. Mobile display ad spending in the U.S. will balloon to $14.67 billion this year, surpassing desktop, where spending will total $12.38 billion, for the very first time, according to eMarketer's projections.

Both Facebook and Twitter will benefit from the shift in ad spending. By 2017, the social networks will collectively account for 33.7% of the $37.36 billion U.S. digital display advertising market.