Sunnyvale, Calif.--Yahoo! Inc. announced Tuesday the appointment of former ZDNet and CNET Networks executive Daniel Rosensweig, 41, as COO. He will report to chairman-CEO Terry Semel and will oversee the operations of Yahoo! worldwide, including product development and marketing. Rosensweig will assume his duties May 13. Most recently, Rosensweig was president of CNET Networks, where he was a key participant in the development of new Internet advertising formats, such as interactive messaging units. Prior to ZDNetâs acquisition by CNET, Rosensweig was president-CEO of ZDNet Inc. from 1997 to 2000.