As emerging Web technologies fuel the rise of so-called social media (think YouTube, MySpace, and Twitter), the practice of interaction design is evolving from its roots in human-computer interfaces to address a broader range of human-to-human activities. Designers who once trafficked in task analysis and usability heuristics now frequently grapple with subtler, “squishier” modes of interaction: negotiating social relationships, building communities, working with issues of trust and identity. From the proliferation of blogs to Facebook, intranets to the endless stream of “crowdsourcing” applications, modern software design seems less predicated on how people interact with computers, and instead focuses more on how people interact with each other …