"Altmetrics" refers to methods of measuring scholarly impact using Web-based social media. Why does it matter? In many academic fields, attaining scholarly prestige means publishing research articles in important scholarly journals. However, many in the academic community consider a journal's prestige, which is determined by a metric calculated using the number of citations to the journal, to be a poor proxy for the quality of the individual author's work. At the same time, hiring and promotion committees are looking for ways to determine the impact of alternate formats now commonly used by researchers such as blogs, data sets, videos, and social media. The panelists all work with innovative new tools for assessing scholarly impact. They are: Jason Priem, Co-Founder, ImpactStory; Kristi Holmes, Bioinformaticist, Bernard Becker Medical Library, Washington University in St. Louis School of Medicine; and Caitlin Aptowicz Trasande, Head of Science Metrics, Digital Science.