The potential advantages of tagging have been addressed in numerous literatures. However, the effectiveness of tagging in information retrieval has not yet been confirmed. There is continuous intensive debate between advocates of new tagging systems and those of traditional controlled vocabulary metadata. Despite all the potential advantages of tagging, the overlapping ratios between tags and the words used in other metadata fields, such as title and description, are significant. In this study, with the data from Youtube.com videos, the degree of overlapping is examined among the fields of title, description and tag, with additional questions about tagging, such as changes in numbers of words in each metadata field over time and the difference between web site promotion videos and non-promotion videos.