Yahoo may be pushing ahead with its strategy to open itself up to outsiders (this weekend was Hack Day ), but insiders are still streaming out the door. Even some of the product managers driving the open strategy are not sticking around. We have learned that Amit Kumar, the director of product management behind Yahoo's Search Monkey and semantic Web initiatives, is leaving by the end of the week. He will be joining semantic Web startup Dapper as Vice President of product management.