The fact that billionaire investor Peter Thiel sold the majority of his stake in Facebook shouldn’t worry investors, but the social network’s mobile problem certainly should, BTIG's Richard Greenfield told CNBC’s “Squawk on the Street”Tuesday.
"I'm not really concerned by him selling specifically, what concerns us is the actual growth trajectory of Facebook ," Greenfield said. "The real challenge they are facing is how do they reach consumers in a mobile world."
It was revealed Monday that Thiel, a Facebook director, sold about 20 million Facebook shares last Thursdaywhen the lock-up expired, according to a filing with the U.S. Securities and Exchange Commission. Thiel is keeping 5.6 million shares.