That leads to Amazon, he said, pointing out that the Internet giant has strong market share positions in retail, as well as marketplace, device and cloud infrastructure businesses.
"It's hard not to be long Amazon," Mahaney said.
People should be aware, however, of the big investments Amazon is making in China and in devices, Mahaney said, as that may mean an Amazon smartphone. In the past, its heavy investments have dented margins.
The company does some strange things, too. For example, original video content is "one of the most unusual investments I've seen them make," he said.
Talking about Yahoo, Mahaney said turning around the company would take at least two years.
"I don't think you're going to see a fundamental improvement in engagement, in display ad revenue until 2014," he said.
The market is not buying into a turnaround yet, either.
"The core business is trading at two or three times cash flow, which is a pretty significant discount," Mahaney said. "We interpret that as the market doesn't believe in the turnaround, which at the margin makes the shares a bit of a safe long."
He said he has an "outperform" rating on Yahoo stock with a $24 price target, adding that "it's a small 'buy' for us, though."