"This is awesome. I didn’t even know it existed” until just recently. That’s how a lot of people are reacting to Clubhouse, the social-media startup that’s becoming a sensation. Except in this case, the new fan was Elon Musk, who had just made his first appearance on the app, a voice-and-audio driven platform that lets people hold live discussions based on any number of topics and interests, with thousands sometimes in attendance.

Musk was a Jan. 31 guest on "Good Time,” a talk show co-led by a panel of venture capitalists and a Facebook Inc. tech executive. Days later, Facebook Chief Executive Officer Mark Zuckerberg made a surprise appearance on the same program. Last month, I wrote about how Clubhouse was poised to become the next big social media powerhouse, citing the doubling of its weekly active user base to 2 million over a couple of weeks in January as a sign of its booming popularity.

This latest wave of influential new users — from technology titans such as Musk and Zuckerberg to political figures and leaders in entertainment — is driving another wave of exponential growth for Clubhouse, not only in the United States but around the world.