Republican senators hinted at a hearing about Facebook data usage on Tuesday that they may be considering antitrust charges against the world’s largest social media platform.

Sen. Orrin Hatch (R-Utah) surely struck fear in the heart of Facebook CEO Mark Zuckerberg by noting that “this is the most intense public scrutiny I’ve seen for a tech-related hearing since the Microsoft hearing I shared in the 1990s.”

Those hearings, of course, focused on Microsoft’s anti-competitive practices, which ultimately led to Microsoft being charged with violating the Sherman Antitrust Act. The company eventually agreed to settle with the Department of Justice and agreed to a major overhaul of their business practices.

Was Hatch’s comment a veiled threat?

There were more antitrust rumblings from Sen. Lindsey Graham, who asked Zuckerberg bluntly: “Who’s your biggest competitor?”

Zuckerberg said that Facebook has plenty of competitors, noting that their customers use an average of eight other apps.

Graham drilled down, asking if those other apps provide the same product. Zuckerberg ticked off some of his competitors.

“You don’t think you have a monopoly?” Graham demanded.

“It certainly doesn’t feel like that to me,” Zuckerberg responded.

“My point is that one way to regulate a company is through competition,” Graham said. “What do we tell our constituents given what’s happened here, why you should self-regulate?”

“My position is not that there should not be more regulation,” Zuckerberg admitted.

He agreed to send the committee some “proposed regulations” that the company would support.

Zuckerberg is on the hot seat today for Facebook’s opaque privacy practices and in some cases misuse of user data. But the line of questioning from Graham and Hatch may indicate that the company has much bigger problems—which could ultimately lead to the breakup of the mammoth company.