Yahoo! made a well-received choice in longtime Google executive Marissa Mayer as CEO, but the task awaiting her is monumental and will require patience, says venture capitalist Marc Andreessen. "Apple demonstrates that it's possible to turn a tech company around. Apple also proves how hard it is because it is one of a very small number of examples. ... It's three to five years to do the job. So one of the things she needs [is] for the board to support her for that period of time," he says.