Social software connects people and information via online, informal Internet networks. Social software can be used by governments for content creation, external collaboration, community building, and other applications. The proliferation of social software has ramifications for U.S. national security, spanning future operating challenges of a traditional, irregular, catastrophic, or disruptive nature. Failure to adopt these tools may reduce an organization's relative capabilities over time. Globally, social software is being used effectively by businesses, individuals, activists, criminals, and terrorists. Governments that harness its potential power can interact better with citizens and anticipate emerging issues. Security, accountability, privacy, and other concerns often drive national security institutions to limit the use of open tools such as social software, whether on the open web or behind government information system firewalls. Information security concerns are very serious and must be addressed, but to the extent that our adversaries make effective use of such innovations, our restrictions may diminish our national security. This analysis looks at both sides of what once might have been called a "blue-red" balance to investigate how social software is being used (or could be used) by not only the United States and its allies, but also by adversaries and other counterparties. We have considered how incorporation of social software into U.S. Government (USG) missions is likely to be affected by different agencies, layers of bureaucracy within agencies, and various laws, policies, rules, and regulations. Finally, we take a preliminary look at questions like: How should the Department of Defense (DOD) use social software in all aspects of day-to-day operations? How will the evolution of using social software by nations and other entities within the global political, social, cultural, and ideological ecosystem influence the use of it by DOD? How might DOD be affected if it does not adopt social software into operations? In the process, we describe four broad government functions of social software that contribute to the national security missions of defense, diplomacy, and development: Inward Sharing, or sharing information within agencies; Outward Sharing, or sharing internal agency information with entities beyond agency boundaries; Inbound Sharing, which allows government to obtain input from citizens and other persons outside the government more easily; and Outbound Sharing, whose purpose is to communicate with and/or empower people outside the government. Social software, if deployed, trained on, monitored, managed, and utilized properly, is expected to yield numerous advantages: improve understanding of how others use the software, unlock self-organizing capabilities within the government, promote networking and collaboration with groups outside the government, speed decision making, and increase agility and adaptability. Along with the accrual of positive benefits, incorporating social software into day-to-day work practices should also decrease the probability of being shocked, surprised, or outmaneuvered. Whether it is misinformation about U.S. actions overseas being spread through new media channels, or new forms of terrorist self-organization on emerging social networks, experimenting with and understanding social software will increase USG abilities to deal with complex, new challenges. Because social software can add significant value to many ongoing missions, and because citizens, allies, and opponents will use it regardless, this paper recommends that national security institutions, particularly DOD, embrace its responsible usage.