Facebook (META -0.43%) CEO Mark Zuckerberg has just undergone two days congressional grilling, and several lawmakers homed in on the company's overwhelming market power and influence in the social media sector. Generally speaking, companies don't like being called monopolies because of the implicit threat of antitrust regulation the word carries. While Facebook would likely fail any official measure (such as the Herfindahl-Hirschman Index) of being a monopoly, there's no question that Facebook dominates the social media landscape.

However, in defending Facebook's position to lawmakers, Zuckerberg just cited its own apps and services as competition.

Mark Zuckerberg speaking on stage

Mark Zuckerberg. Image source: Facebook.

Facebook-owned services dominate the charts

Responding to Republican Senator Lindsey Graham yesterday regarding Facebook's market power, Zuckerberg replied, "The average American I think uses eight different communication and social apps. So there's a lot of different choice and a lot of innovation and activity going on in this space."

It's not clear which specific apps Zuck is referring to, but there should be little doubt that Facebook owns several of them. For example, among the top 10 free apps in the iOS App Store right now, you'll find Instagram (No. 1), Messenger (No. 3), and the core Facebook app (No. 5). Additionally, Facebook is developing its Watch platform, which it hopes will compete with Alphabet's YouTube, the No. 2 free app. Snap's Snapchat sits at No. 4, and Facebook is relentlessly trying to destroy Snapchat by replicating its most popular features.

Within the social networking section, Messenger is No. 1, followed by Facebook at No. 2 and WhatsApp at No. 3. (Instagram is technically categorized as "Photo and Video.")

Facebook is becoming a social media conglomerate

Over the years, after ruthlessly consolidating power within the social media sector, either by scooping up smaller rivals or copying features to aggressively compete, Facebook has effectively become a social media conglomerate, operating a diverse and growing portfolio of brands under its corporate umbrella. While many of these subsidiaries have varying levels of independence and autonomy, they still ultimately answer to His Zuckness, and their financial results are consolidated within one company.

Social media falls under the broader market of digital advertising, which is largely a duopoly led by Google. Facebook and Google's combined share of that market is expected to decline in the years ahead, according to recent estimates from eMarketer. That could potentially mitigate the risk of regulators stepping in. Still, just like my Uncle Ben used to tell me, "With great power comes great risk for regulatory oversight."