Presented at the 32nd Research Conference on Communication, Information and Internet Policy (Telecommunications Policy Research Conference 2004) held at the Tech Center, George Mason University, U.S.A, October 1-3, 2004. An earlier version of the paper was presented at SNU Center for Law & Technology's 2004 International Symposium in Seoul : Beyond Property v. Commons Dimension for a New Spectrum Management System, held in Seoul, Korea August 16, 2004.