Shares of social media giant Facebook Inc. (FB) continue on their downward spiral this week, trading down 6% on Monday morning and falling below $150 a share for the first time since last July. The Cambridge Analytica scandal has wiped out nearly $100 billion in market for the social media company since March 16. The stock has officially sunk into bear market territory on news that that U.S. regulators have confirmed previous reports of a non-public investigation into the Silicon Valley company's privacy practices. 

FTC Confirms Probe After Massive Data Scandal 

FB stock now reflects a near 23% decline from its 52-week high of $195.32, according to data from FactSet. Shares of the social network closed at a record high of $193.09 on February 1 after posting fourth quarter earnings above Street estimates, despite reporting its lowest quarter-over-quarter (Q/Q) percentage daily user growth ever.

Facebook's plummet into bear market territory, typically defined as a drop of 20% or more from a peak, has been driven by criticism over how the company manages its data. On Monday, the stock suffered its worst day in four years after it was reported that data analysis firm Cambridge Analytica allegedly used information on more than 50 million users without their consent to help the Trump campaign in the 2016 U.S. presidential race. The stock continued to fall last week as a #DeleteFacebook campaign gained momentum, solidifying its worst one-week decline in six years. 

Graph source: FactSet

On Monday, the sell-off was amplified by reports that the Federal Trade Commission (FTC) is investigating Facebook regarding whether the company violated a consent decree that the tech firm signed with the agency in 2011. The consent decree required that Facebook notify its users and receive explicit permission before sharing personal data beyond their specified privacy settings.

Facebook, among the worst performing companies in the S&P 500, is down 14.4% year-to-date (YTD), versus the S&P 500's 2% decline and the Nasdaq Composite Index's 2.4% increase over the same period. 

In response to the wave of negative media, Chief Executive Officer (CEO) Mark Zuckerberg came out with a personal apology, indicating that he is happy to testify in Congress and is preparing to spend many millions to fix issues. The company took out full-page ads in nine newspapers across the U.S. and the U.K. this weekend to apologize for a "breach of trust."