According to Bloomberg, a sell-off sent the tech giant's shares down 4.9 percent on Monday, adding to a drop of about 15 percent since mid-September.

The stock decline on Monday sent Mark Zuckerberg's value down to $121.6 billion, down from Microsoft founder Bill Gates in No. 5 on the Bloomberg Billionaires Index.

Mark Zuckerberg had $140 billion in September, according to the index.

On September 13, The Wall Street Journal began publishing a series of stories based on internal social media documents, revealing that Facebook was aware of issues with its products – such as Instagram's harm to mental health in teenagers and the disinformation about the attack on the Capitol of the United States of America (USA).

The reports – put into perspective by Facebook in public – caught the attention of congressmen and, on Monday, a former employee of the company declared herself to be the complainant in the case to the press.

In response, Facebook emphasised that the problems of its platforms, including political polarisation, are complex and, he warned, not just caused by technology.

"I think it comforts people to assume that there must be a technical explanation for the issues of political polarisation in the US," Nick Clegg, Facebook's vice president of global affairs, told CNN.

In Portugal, platform problems began to be felt significantly from 16:30 (Lisbon time) on Monday, with services only resuming from 23:00.