Online traffic watcher comScore says that Facebook showed 30 percent of all the online display ads in the U.S. in the first quarter. That was three times as many as Yahoo, and at least six times as many as Microsoft, AOL, and Google. (These are ads shown on company-owned sites, not their ad networks.) Alas for Facebook, it’s still getting far less money per impression than the other guys. That’s partly because it doesn’t have a big rich-media ad unit to sell and partly because advertisers correctly devalue ads shown next to communications. Facebook has a new ad format that actually takes advantage of social media by highlighting friends’ actions to friends, and it shows some promise, although I’d be cautious about overreacting to something that still has a novelty factor going for it. Meanwhile Facebook’s ad ecosystem continues to show action, as search and performance marketing firm Efficient Frontier buys a Facebook social marketing specialist.