US government regulators have been watching with interest as Facebook's troubles keep piling up, and now the Federal Trade Commission (FTC) is adding to them. The agency, which is tasked with protecting consumers from abusive business practices, has announced that it has opened an investigation of Facebook's handling of user privacy.

According to the FTC, there is an ongoing non-public investigation of the social network. As such, details of the investigation are scarce. However, the FTC notes the issue is related to recent media reports of Facebook's lax privacy practices. It allowed consulting firm Cambridge Analytica to collect data on some 50 million users, and recent reports indicate it sneakily vacuumed up more data than it should have via Android permissions. Although, the latter issue seems to have been blown out of proportion.

Facebook's stock price has slipped another 3% on the news, leaving the company's stock down around 16% in the last few weeks. If the FTC finds Facebook failed to adequately protect its users, it could be fined as much as $40,000 per violation. That could, theoretically, mean a $2 trillion fine. That's obviously not going to happen, but the FTC could still hit Facebook with a big bill to pay.