Editor's Note: This article was originally published on Real Money at 1:55 p.m. on July 28.
The Citron Research founder confirmed that he does have a small position that is short Facebook. "The dynamic is you need to find the new incremental buyer," Left said in a phone interview with Real Money Thursday. Left recently told CNBC that he was short the social network's shares, citing its diminished relevance among younger users.
Facebook stock jumped about 1% higher Thursday to $124.69 based on quarterly results released late Wednesday that exceeded expectations for nearly every metric. Revenue rose 59% year over year, ad sales rose 63% this quarter, monthly active users rose 4% quarter over quarter and 15% annually, while daily active users rose 4% quarter over quarter and 17% from a year ago.
The social media company's business model relies on users sharing personal data. But Left said there is an inherent flaw in CEO Mark Zuckerberg's business model. While Facebook is great for connecting with people, the short-seller said children don't want to share everything with everyone anymore. Left added that the Pokemon Go craze is evidence that people want to use their phones for something other than Facebook or Instagram.
"The key thing is engagement, how much time people spend on the platform," Left said.
Analysts with Jefferies said the larger question is Snapchat's rapid rise and the effect on Facebook's Instagram. They argue that the image-messaging app could affect 3% to 9% of Facebook's 2018 earnings per share, and those effects could materialize as early as the fourth quarter this year.
Meanwhile, analysts at Pacific Crest Securities said in a research note Thursday that Facebook is the largest social network in the world and does not have any competition on a global user level. But under the analysts' bear case, they noted that user growth has to slow and ad load may have to grow slowly to protect user experience. Still, the analyst team said it is "impossible to deny Facebook's momentum" and raised their revenue estimate to $27.4 billion from $26.2 billion.
The Pacific Crest analysts were not alone in raising their numbers for Facebook either. Deutsche Bank increased its estimates; Cantor Fitzgerald, Wedbush, Piper Jaffray and Morgan Stanley all raised their price targets; Oppenheimer raised both its estimates and its price target.
"Anytime you can almost triple your earnings, anytime you have accelerated revenue growth for a company this size, anytime you see the whole future coming, it really is a rather remarkable company, " said TheStreet's Jim Cramer Thursday on CNBC's Squawk Box. "This is just one of the great growers, it's so, so impressive."
Facebook is a holding in Cramer's Action Alerts PLUS portfolio.
While the analysts and Cramer appear bullish on Facebook, Left believes the stock could go the way of Apple (AAPL) - Get Report a few years ago. He said when Apple stock was at $700, people were wondering when it would go to $1000, but then it became cheap. (Apple is another holding in Action Alerts PLUS).
Facebook stock will fall, Left said, but he cannot pick what quarter that will happen.
The short-seller also clarified his comments to Bloomberg from earlier in July, when he said Facebook could lose nearly a third of its value. He told Real Money Thursday that if Facebook's value fell 30%, it "can still do all the same great things, just at a lower market cap."
All that being said, Left added that he believes Facebook is "a great company."