We examine tagging behavior on Flickr, a public photosharing website. We build on previous qualitative research that exposed a taxonomy of tagging motivations, as well as on social presence research. The taxonomy suggests that motivations for tagging are tied to the intended target audience of the tags - the users themselves, family and friends, or the general public. Using multiple data sources, including a survey and independent system data, we examine which motivations are associated with tagging level, and estimate the magnitude of their contribution. We find that the levels of the Self and Public motivations, together with social presence indicators, are positively correlated with tagging level; Family & Friends motivations are not significantly correlated with tagging. The findings and the use of survey method carry implications for designers of tagging and other social systems on the web.