AT&T's proposed acquisition of T-Mobile presents an opportunity for judicial scrutiny of the newest iteration of the Department of Justice ("DOJ") and Federal Trade Commission's (FTC's) Horizontal Merger Guidelines ("2010 Guidelines"). The Agencies revised the 2010 Guidelines with an eye toward increasing transparency and predictability by conforming them to actual agency analysis. The 2010 Guidelines highlight the Agencies' adoption of a more economically sound analytical approach focusing directly upon the competitive effects of proposed mergers and de-emphasizing the importance of market definition and competitive inferences from market structure. But, oddly, the DOJ's complaint reverts to its pre-revision approach, emphasizing a remarkable focus upon market definition and structural analysis. The structure-heavy approach the DOJ adopts in its complaint runs afoul of the standards it espouses in the Guidelines, raising the risk of undermining their continued success as measured by judicial adoption.