Matthew Ingram sketches out why Yahoo should fear Facebook more than Google. (Yesterday Yahoo CEO Carol Bartz said at an event that Facebook was the bigger threat.) Both Yahoo’s and Facebook’s revenues depend on brand advertisers, and both want to hold their audiences’ attention. But Google’s the one with the competitive ad network. Bartz is right: In brand advertising, more of the money stays with the company that owns the ad inventory than goes to the network. Earlier, I wrote how Yahoo could inject a jolt of social into its bloodstream. Google’s eager to do so as well, but if this is its master plan, it needs a lot of work.