Web 2.0, the Social Web, offers unparalleled opportunities for people to network and collaborate. The advent of Web 2.0 as a commerce engine, however, brings unique challenges to the lofty purposes upon which social networks were created. Facebook's disastrous IPO might turn out to be a fluke, but it sends a strong signal that big-brand advertising might not be entirely suitable in the social context. Moreover, existing technology might not be sufficiently optimized or scaled to deliver the kinds of data necessary to support near real-time commercial opportunities. Thoughtful Web 2.0 critics express grave concerns over the loss of privacy and the need to exercise "individual liberty." The promise of Web 3.0, based on the notion of trust, might put some of these concerns to rest, but at the end of the day, the social Web is about community, not universality. This department is part of a special issue on social media.