It's not a great time to own Facebook stock.

The social media company's market valuation fell by roughly $40 billion on Monday following the revelation that the Trump-linked, U.K.-based company Cambridge Analytica harvested information from 50 million Facebook profiles without user consent.

The company's stock price was down 6.8 percent by the end of the day, marking the worst day the stock has had since March 2014.

The decline is one of the biggest percentage drops to ever occur for the social network's stock, and according the Wall Street Journal, the decline also knocked Facebook out of the S&P 500's five biggest market caps. The distinction of the S&P 500's biggest five is now held by Apple, Google's parent company Alphabet, Amazon, Microsoft, and Berkshire Hathaway.

Facebook's stock price took a dive Monday morning. The company's market valuation declined by about $40 billion. Image: screenshot / Google finance

To add to the debacle, Facebook's chief information security officer Alex Stamos announced late Monday he's leaving the company over "internal disagreements" about how the company is responding to its role in spreading disinformation, according to a New York Times report. Stamos was reportedly a strong advocate for investigating and disclosing Russian activity on Facebook, but found himself at odds with other senior executives, including COO Sheryl Sandberg.

But all this may be the least of Mark Zuckerberg's worries. The company's founder lost about $4.9 billion on Monday according to a Bloomberg report. The slump in net worth drops Zuckerberg to only the fifth wealthiest man in the world behind Jeff Bezos, Bill Gates, Warren Buffet, and Amancio Ortega.

It's important to note that other big tech companies also had a rough Monday. Apple, Alphabet, Microsoft, and Amazon share prices all dropped by more than 1.5 percent. The S&P 500 was down 1.3 percent on the day.