Social network sites (SNSs) have the potential to fundamentally change the character of our social lives, both on an interpersonal and a community level. Changes in interaction patterns and social connections are already evident among young people, who are the heaviest users of these sites. As adoption spreads to a wider audience, we expect such changes to be amplified across all segments of society. At an interpersonal level, the identity information included in public profiles serves to lower the barriers to social interaction and thus enable connections between individuals that might not otherwise take place. On a community level, the organizing features of these sites lower the transaction costs for finding and connecting with others who may share one interest or concern but differ on other dimensions. Both of these processes have the potential to have positive effects on society at large because they encourage disparate individuals to connect, communicate, and take action.