No procedural topic has garnered more attention in the past fifty years than the class action and aggregation of plaintiffs. Yet, almost nothing has been written about aggregating defendants. This topic is of increasing importance. Recent efforts by patent “trolls” and Bit-Torrent copyright plaintiffs to aggregate unrelated defendants for similar but independent acts of infringement have provoked strong opposition from defendants, courts, and even Congress. The visceral resistance to defendant aggregation is puzzling. The aggregation of similarly situated plaintiffs is seen as creating benefits for both plaintiffs and the judicial system. The benefits that justify plaintiff aggregation also seem to exist for defendant aggregation—avoiding d...