This paper presents a framework model that defines learning and knowledge building as a co-evolution of cognitive and social systems. This model brings together Scardamalia and Bereiter’s theory of knowledge building and Nonaka’s knowledge creation theory. We demonstrate how learning and knowledge building may occur when people interact with each other, using shared digital artifacts such as tag clouds (that result from social-tagging activities) or wikis. For both technologies, we provide illustrating data from two pilot studies. As an example, we refer to the learning processes that take place while searching for information in tag clouds. In addition, we illustrate processes of knowledge building by referring to users working on a wiki. In conclusion, the differences and similarities between these technologies are assessed, regarding their potential for knowledge building.