The U.S. Federal Trade Commission took a major step toward the possible breakup of Facebook Inc. by formally filing an antitrust lawsuit against the technology giant, accusing it of abusing its monopoly powers in social networking to stifle competition.

The FTC and a coalition of states also suing the company zeroed in on Facebook’s acquisition of photo-sharing app Instagram for $715 million in 2012, and the $22 billion deal for messaging service WhatsApp two years later. The deals, which sailed past regulators when they were proposed, were meant to “squelch” competitive threats, the commission wrote in its complaint Wednesday. Now, the FTC wants Facebook to divest the two businesses -- an idea that poses an existential threat to the empire built by Chief Executive Officer Mark Zuckerberg.

Because much of the company’s revenue growth is already coming from Instagram, and WhatsApp is central to Facebook’s bet on digital commerce, losing the two platforms would threaten to erase much of Facebook’s long-term value. The company’s shares, which have soared more than 35% in 2020, fell as much as 4% Wednesday, ending the trading day down about 2%.

Breakups are scary for investors because in some ways they could disrupt the business models,” said Dan Ives, an analyst at Wedbush Securities who called Instagram one of the three best business acquisitions of the past 15 years. Still, Ives thinks the chance of an actual breakup is “slim” without legislative changes from Congress, which he believes are unlikely. “It’s a noisy headline but it doesn’t massively change the situation for Facebook in the near term.”