Facebook shares have plummeted to a four-year low, dragging numerous US financial indexes down with it.

The stock price had dropped 6.8% to $172.56 at the closing bell, which is its biggest one-day loss since March 2014.

The share price drop came hot on the heels of reports that a UK-based data-mining firm Cambridge Analytica, harvested the data of 50 million Facebook users without neither their knowledge or consent.

In a report at the weekend in The Observer, Cambridge Analytica founder turned whisteblower, Christopher Wylie, went public with the story, revealing that the firm was funded by the billionaire Mercer family, who similarly backed conservative website, Breitbart, and that at one time, it was headed up by former Trump advisor, Steve Bannon.

Wylie also revealed that Facebook made “zero effort” to get the data back that Cambridge Analytica had illicitly harvested. Facebook has since banned Wylie from its platforms.

Both US and UK authorities have launched investigations into Cambridge Analytica to find out whether the firm’s work violated data protection laws on both sides of the pond.

According to reports, Cambridge Analytica was hired by the Trump campaign in 2016, in order to target adverts using the data the firm had collected. Cambridge Anlaytica also helped the Leave campaign in the run-up to the EU referendum in the UK.


[Image – CC BY SA 2.0 Esther Vargas]