The article aims to study folksonomy in the view of knowledge representation. A bibliographic review of the approaches to knowledge organization proposed by Hjorland is conducted in order to find out how folksonomy can be matched. The approaches are: user-based, cognitive, social and information retrieval approach. The article also includes a brief discussion about knowledge organization and information organization, defining how those concepts will be addressed in the article. It highlights the positive and negative aspects of folksonomy as a knowledge representation scheme, and it also analyzes how it can reflect or fail to reflect knowledge. In addition, it identifies folksonomy as a system designed differently than other systems, in which term collections and structure is done a posteriori. It sets folksonomy in the representation schemes, in order to be considered a semantic tool. It suggests new studies to compare folksonomy to the traditional knowledge representation schemes, such as thesauri, taxonomies and ontology.