First Author:   Yan Chen University of Michigan yanchen@umich.edu   School of Information, 1075 Beal Avenue Ann Arbor, 48109, U.S.A.   734 764 9488(Phone) 734 764 9488(Fax) www.si.umich.edu/~yanchen Second Author: Teck-Hua Ho University of California at Berkeley hoteck@haas.berkeley.edu   Haas School of Business, University of California Berkeley, 94720-1900, U.S.A.       Third Author: Yong-Mi Kim University of Michigan kimym@umich.edu   School of Information, University of Michigan, 1075 Beal Avenue Ann Arbor, 48109, U.S.A.