Sharing scientific research data has become increasingly important for knowledge advancement in today's networked, digital world. This article describes the evolution of access to United States government information in relation to scientific research funded by federal grants. It analyzes the data sharing policy of the National Science Foundation, which requires inclusion of a Data Management Plan in research proposals seeking agency funding. This policy is compared to a similar policy of the National Institutes of Health. Eight key issues limiting the success of the National Science Foundation policy are identified. These issues derive from instances of ambiguity, contradiction, inconsistency, lack of clarity, and gaps in guidance. Academic librarians can help fill the gaps in data sharing policy guidance by assisting researchers in the development of Data Management Plans and facilitating implementation of data curation practices.