The latest advertising data from comScore shows that Facebook was the largest display ad publisher in the U.S. during the first quarter of 2010. The social networking site displayed an estimated 176 billion impressions from January through March, accounting for 16 percent of the total number of advertisements served to users.

Yahoo-owned properties accounted for 12.1 percent of all online ads for the quarter, displaying an estimated 132 billion impressions. Yahoo, Microsoft, Fox Interactive Media and AOL properties all saw their numbers drop from the fourth quarter of 2009 while Facebook’s ad impressions have grown by 52 percent in that period.

The numbers reveal nothing about the revenue generated from all those ad impressions, but it is clear that social networks and Facebook in particular has become the preferred target among online marketers.