The pressure is on Yahoo CEO Marissa Mayer to explore a tie-up with AOL. Activist investor Starboard Value has taken a significant stake in Yahoo and is pushing the company to cut costs. In the more than 2 years since Marissa Mayer took over the reigns at Yahoo, the company has acquired about three dozen companies large and small. Starboard chief Jeffrey Smith believes those acquisitions made no difference in attracting advertisers and only piled on costs. However, he thinks a tie-up with AOL will bring growth. AOL is worth $3.5 billion, just within Yahoo's budget of $5 billion that it will receive from selling a portion of its stake in Alibaba. Mayer responded diplomatically and didn't close the door to any move. She said, 'We have maintained, and will continue to maintain, an open dialogue with all. As part of our regular evaluation of Yahoo's strategic initiatives to drive sustainable shareholder value, we will review Starboard's letter carefully and look forward to discussing it with them.' Mayer has been relying on acquisitions to add small teams of engineers. The hope there is these nimble teams of engineers will build new designs and platforms to attract more users quickly.