In the face of data mining charges flying high, Facebook founder Mark Zuckerberg has admitted that the social network "made mistakes" that led to millions of it's users having their data exploited by a political consultancy.
Cambridge Analytica (CA) is accused of improperly using the data on behalf of political clients.
In a statement, Zuckerberg said a "breach of trust" had occurred.
In a later interview, he said he was "really sorry," and pledged to take action against "rogue apps".
He added that he was "happy" to testify before American Congress "if it's the right thing to do".
In his statement posted on Facebook, he promised to make it far harder for apps to "harvest" user information.
"We have a responsibility to protect your data, and if we can't then we don't deserve to serve you," Zuckerberg said.
As the controversy snowballed over hijacked personal data, a movement to quit the social network has gathered momentum, getting a boost from a high-profile co-founder of the WhatsApp messaging service acquired by the huge social network in 2014.
"It is time #deletefacebook," Brian Acton said in a tweet, using the hashtag protesting the handling of the crisis by the world's biggest social network.
The WhatsApp co-founder, who now works at the rival messaging application Signal, posted the comment amid a growing uproar over revelations that Facebook data was harvested by a British political consulting firm linked to Donald Trump's presidential campaign.
"Delete and forget. It's time to care about privacy," he said.
Several websites offered tips on how to quit Facebook, while noting that the process is more complicated than it appears.
Facebook offers users the option to "deactivate" an account for users who want to take a break and return later, or to "delete" the account and its data entirely.
But Facebook noted that some data such as posts on friends' timelines might remain in the system even after an account is deleted.
India's Information Technology minister warned against any abuse of social media in elections.
India is due to hold a national election in 2019 and several states will elect new assemblies this year and next.
"Abuse of social media including Facebook cannot be allowed to impact the fairness of elections," Ravi Shankar Prasad said.
"In the wake of recent data theft from Facebook, let my stern warning be heard across the Atlantic, far away in California. Any covert or overt attempt to misuse social media including Facebook to influence India's electoral process through undesirable means will neither be tolerated, nor be permitted."
Facebook said Prasad had raised several important questions and the company appreciates his attention to this matter.
"We will continue to engage with the government on this matter. We are committed to vigorously enforcing our policies to protect peoples' information and will take whatever steps are required that this happens," the company said in a statement.
The psychologist at the centre of a scandal over the misuse of millions of Facebook users' personal data worked with Russian researchers on a study of pathological personality traits.
Aleksandr Kogan advised a team at St Petersburg State University that was exploring whether psychopathy, narcissism and machiavellianism - dubbed the 'dark triad' by psychologists - were linked to abusive online behaviour, said Yanina Ledovaya, senior lecturer at the university's department of psychology.
"We wanted to detect (internet) trolls in order to improve in some way the lives of people suffering from trolling," Ledovaya said.
As the issue rages further, EU leaders due to meet in Brussels this week will discuss the scandal over harvested data from Facebook, President Donald Tusk said, linking it to the broader threats including election meddling.
Tusk said the summit would deal with issues of personal privacy raised by the row over the misuse of Facebook data by the British firm, which played a role in Trump's election campaign.
He said the poisoning of a Russian ex-spy in Britain earlier this month, which London blames on Moscow, shows that "we need to increase our resilience to hybrid threats, such as undermining trust in our democracies through fake news or election meddling".
"This seems to be particularly relevant in view of the recent revelations about Cambridge Analytica," said Tusk, the summit host as head of the European Council, which groups the 28 member states.
Adding fuel to the fire, an Austrian privacy campaigner said Facebook was warned in 2011 of the loopholes exploited by UK data firm Cambridge Analytica but said it saw no need to change its policies.
Max Schrems, an activist who has brought several cases before European courts to strengthen data protection online, said that the controversial data harvesting methods at the centre of the current scandal were exactly those he had raised in a complaint before the Irish Data Protection Authority in 2011.
The current scandal centres on an app which its developer says was used by 200,000 people, but which saw around 30 million US Facebook users' details harvested.
The app's vast reach beyond its users was due to it scooping up data from users' friends on Facebook.
Zuckerberg meanwhile, has vowed to "step up" to fix problems at the social media giant, as it fights a snowballing scandal over the hijacking of personal data from millions of its users.
"Our responsibility now is to make sure this doesn't happen again."
He announced new steps to rein in the leakage of data to outside developers and third-party apps, while giving users more control over their information through a special toolbar.
But it needs to be seen how Facebook will do it, but before that it has lost it's face value!