Facebook shares had their worst day of the year on Monday, closing down 3.3 percent and extending last week's losses.
The drop came after the company lost its chief product officer, Chris Cox, last week. Analysts at Needham downgraded the stock on Monday over growing concern that more top executives could follow the leads of Cox and Chris Daniels, the head of WhatsApp, who also resigned.
Cox, one of the earliest Facebook employees and someone insiders called the "heart and soul of the company," left as CEO Mark Zuckerberg decided to shift the company's focus towards private messaging instead of open posts on the News Feed.
The stock dropped 2.5 percent on Friday and is down more than 13.3 percent over the past year.
Facebook's move towards private communication could also have investors concerned how its massively profitable targeted advertising products will work if users aren't posting publicly. Zuckerberg has said on recent company earnings calls that the company is still thinking of ways to advertise in products like Stories, which features content that disappears after a day. Zuckerberg also said it will take a long time to integrate its various messaging products like WhatsApp and Instagram into the broader Facebook ecosystem.
Also last week, Facebook faced criticism for the spread of videos showing the shooting at a mosque in New Zealand. The shooting was initially streamed through Facebook's live feature, and copies of the video spread throughout the social network from other users. Facebook said Saturday that videos of the shooting were uploaded 1.5 million times, but most were removed before they could spread.
There are also regulatory concerns, with some state attorneys general considering taking action against the privacy practices of big tech companies like Facebook and Google, the Washington Post first reported last week.
"You can't allow this power to accumulate in the hands of the few people, at some point, there's going to have to be a reckoning for it," Mississippi Attorney General Jim Hood said on CNBC's "The Exchange" last Friday.