Worries that Facebook and Google hold too much power over the internet are prompting some public calls for anti-monopoly investigations.

On Monday, US Treasury Secretary Steve Mnuchin urged the Justice Department to take "a serious look" at whether tech companies including Google hold a monopoly.

"As these technology companies have a greater and greater impact on the economy, I think that you have to look at the power they have," Mnuchin told CNBC in an interview.

Last night, 60 Minutes also aired a segment that asked how Google got "so big."

On the same day, several activist groups including MoveOn Civic Action and SumOfUS, demanded that the Federal Trade Commission break up Facebook, claiming that it's amassed "a scary amount of power."

"Facebook unilaterally decides the news that billions of people around the world see every day," their campaign claims. "It buys up or bankrupts potential competitors to protect its monopoly, killing innovation and choice. "

The groups have called their movement "Freedom From Facebook," and plan to make a "six-figure ad buy" encouraging the public to sign a petition that calls on the FTC to split up Facebook. Specifically, the movement wants the company to spin off the Facebook-owned Instagram, WhatsApp, and Messenger products into their own competing networks.

"Facebook is too big, controls too much data, and abuses user privacy—among other things. The People deserve a better, more transparent town square," said VP of the Content Creators Coalition John McCrea in a statement.

This backlash comes on the heels of some bad PR for Facebook. In March, news emerged that a UK political consultancy secretly collected data on millions of Facebook users by exploiting the platform's privacy practices.

Although Facebook apologized, the incident fanned some anti-tech sentiments against Silicon Valley, sparking the DeleteFacebook movement that briefly encouraged users to drop the platform. But despite the outrage against the company, it appears that most users are still sticking around.

So far, Google and Facebook haven't responded to calls for anti-monopoly investigations. In Facebook's case, the company has vowed to stop bad actors over the platform. It's also been steadily adding new privacy controls that can limit what personal data is shared to third-party apps and to Facebook itself.

Tomorrow, CEO Mark Zuckerberg is scheduled to appear before the European Parliament to answer questions about the Cambridge Analytica debacle; it will be live-streamed.