Data and information quality (DIQ) have been defined traditionally in an organizational context and with respect to traditional information systems (IS) as, for example, “fitness for use” of data or “intrinsic” DIQ. Numerous frameworks have been developed that operationalize traditional DIQ accordingly. However, over the last decade, social IS such as social media have emerged that enable social interaction and open collaboration of voluntary prosumers, rather than simply supporting specific tasks as do traditional IS in organizations. After reviewing the current definitions of DIQ, we conclude that these definitions do not capture DIQ in social IS well, nor how it is defined, maintained, and improved through social interaction. Hence, we propose a new definition of DIQ in social IS based on the notion of "matching" between dynamic, voluntary, and heterogeneous supply and demand of data/information. We illustrate our definition with an ontological framework and discuss its implications.