Shopping mall magnate A. Alfred Taubman sold half of his shares in Sotheby\'s Holdings Inc. Thursday in a move that ends the Taubman family\'s control of the high-profile auction house after more than two decades. The transaction, which was initiated by Sotheby\'s, was structured as an exchange of the family\'s 14 million Class B shares, for $168 million and 7.1 million shares of common stock. One motivation for the transaction was to simplify corporate governance, said Harvey Kahalas, dean of Wayne State University \'s business school.