"I think there are more interesting stocks in this space," he said. "Priceline is one, Netflix, Amazon. But nonetheless there's open-field running opportunity for a name like Facebook when you've got an inflection point and half the market has caught on to this."
On CNBC's "Fast Money," Mahaney responded to a Twitter user's question about what it would take to raise Facebook's price target.
"We have a $40 price target," he said. "Is that not enough?"
(Read more: Doug Kass on why he ditched Twitter)
Mahaney noted that he had upgraded Facebook's price target when it was at $20.
The internet analyst said that he saw potential upside for the stock.
"This company is now introducing video ads in the back half of this year," he said. "That's a new revenue stream."
(Read more: What'll send Netflix, Yahoo higher: Mark Mahaney)
Facebook's mobile-led growth "probably continues," he added.
Mahaney also pointed out large potential yet unrealized catalysts.
"There's two completely unmonetized assets on the internet today," he said. "Google Maps is one, and Instagram's another."
While Facebook could likely turn its Instagram asset into a revenue stream, Mahaney added that he was sticking with the "small buy" rating for the stock.
(Read more: Facebook's a 'small buy': Mark Mahaney)
But what would define the winners was clear, he said.
"The biggest trend in the internet space right now is mobile, and if you don't have mobile right, your stock gets hit," Mahaney said.
Trader disclosure: On Aug. 7, 2013, the following stocks and commodities mentioned or intended to be mentioned on CNBC's "Fast Money" were owned by the "Fast Money" traders: Tim Seymour is long BAC; Tim Seymour is long TSL; Tim Seymour is long SBUX; Dan Nathan is long FB; Dan Nathan is long JCP; Dan Nathan is long BA; Dan Nathan is long VIX; Dan Nathan is short IWM; Josh Brown is long AAPL; Josh Brown is long XLU; Josh Brown is long FSLR; Josh Brown is long LULU; Guy Adami is long C; Guy Adami is long GS; Guy Adami is long INTC; Guy Adami is long MSFT; Guy Adami is long AGU; Guy Adami is long NUE; Guy Adami is long BTU; Guy Adami's wife, Linda Snow, works at Merck.