Santa Clara, Calif.--Yahoo! Inc. has hired Tiana Wimmer as general manager of direct marketing, a new position. Wimmer, previously VP-consumer card Internet marketing at American Express Co., will oversee all of Yahoo!'s e-mail marketing initiatives. Her appointment comes amid Yahoo!'s ongoing executive shuffle. In recent weeks, CEO Timothy Koogle has resigned and Gregory Coleman, a former top executive at The Readers Digest Association Inc., joined as exec VP-North American operations.