In this paper, we present results of an empirical investigation into the social structure of You- Tube, addressing friend relations and their cor- relation with tags applied to uploaded videos. Results indicate that YouTube producers are strongly linked to others producing similar con- tent. Furthermore, there is a socially cohesive core of producers of mixed content, with smaller cohesive groups around Korean music video and anime music videos. Thus, social interaction on YouTube appears to be structured in ways simi- lar to other social networking sites, but with greater semantic coherence around content. These results are explained in terms of the rela- tionship of video producers to the tagging of uploaded content on the site.