"I am not saying Facebook is a 'bad company' (it) just will not be a $330 billion company in a year," Left told CNBC.
Facebook shares traded down 2.6% Monday midday to $113.59 per share. The company has a market cap of $319 billion.
Cramer did praise Left's prior criticisms of Valeant Pharmaceuticals (VRX) and Wayfair (W) - Get Report but cautioned that in those cases he was able to "come up with something where there was a smoking gun."
"I'm always thinking about the out years and whether Facebook is losing to Snapchat whether Zuckerburg is doing enough to be able to keep the momentum, but ... I know that Andrew is looking at it short term," said Cramer, TheStreet's founder and manager of the Action Alerts PLUS portfolio, which owns FB.
He said the short is mainly based on the short-term outlook for Facebook and that the stock is actually trading below projected 2017 and 2018 numbers.
Separately, TheStreet Ratings team rates the stock as a "buy" with a ratings score of A-.
"Andrew does high quality work," Cramer said. "Is he calling a top so to speak? Well, he did call a bottom on LinkedIn. He did buy LinkedIn when it was lower... I would prefer to see it when he actually has something. But then again, Facebook's run a lot so it's entirely possible you want to make that call."