Facebook in particular is gaining significant market share. In 2012, the social network accounted for just 5.4% of the global advertising market. In 2013, that share increased to 17.5%, and eMarketer predicts it will rise again this year to 21.7%. Google still owns a plurality of the mobile advertising market worldwide, taking a portion of nearly 50% in 2013, but the rapid growth of Facebook will cause the search giant’s share to drop to 46.8% in 2014, eMarketer estimates. Read the rest at eMarketer.