Musk is not an ordinary person using the democratization of self-publishing to reach the masses; he is a very powerful man with access to an exceptionally loud megaphone, and he potentially reaps great financial rewards as a result.

This is not the only recent case in which a celebrity tweet has moved markets: President Donald Trump has often done it, as when he criticized Lockheed Martin’s F-35 fighter-jet program and the stock lost $4 billion in value; earlier this year, the model Kylie Jenner wrote a mildly critical tweet about Snapchat that was credited with inspiring a selloff that lost Snapchat’s parent company, Snap, more than $1 billion.

Musk’s tweet is notable, though, for the one-to-one relationship between his message and his wealth. As it began sending Tesla’s share price up, he tweeted, “Good morning,” with a smiley-face emoji. It was a good morning, for him. Musk owns nearly one-fifth of Tesla; it’s hard to think of anyone who would have benefited more from an 11-percent stock-price gain, at least when it comes to short-term finances. If Twitter’s early executives had hoped that their product would break the hold of the rich and powerful, Musk’s tweet is evidence that the social-publishing platform has done the opposite and, in fact, consolidated their power.

Elon Musk says he wants to make a credibility-ranking site for people to rate journalists and news organizations

There’s no question that Twitter has helped amplify voices that might otherwise be marginalized: The #BlackLivesMatter and #MeToo movements both started there. Still, evidence suggests that Twitter amplifies already-loud voices even more. The largest single-day volume of tweets using Trump’s #MAGA hashtag (about 800,000 on Election Day) was double the single-day record for the anti-Trump #resist hashtag (about 400,000 on the day of Trump’s travel ban, soon after his inauguration). Three years ago, computer scientists at the University of Pennsylvania and elsewhere studied the demographics of Twitter users and found that high earners had more followers and got more retweets than low-income people. Similar dynamics play out in other areas, too. In June, the International Journal of Press/Politics published a study finding that male political reporters retweeted tweets written by male colleagues three times as often as they retweeted female colleagues; female journalists also retweeted men more often. The authors concluded, “Our research … suggests that Twitter reflects (and may amplify) existing gender asymmetry in the power center of U.S. politics.” Complicating matters is the fact that armies of bots are deployed to sow ideological divisions and muddy any authentic sense of which voices are loudest.

This is almost certainly not what Twitter’s founders had in mind when they started the company. But Twitter doesn’t do much to discourage any of it. The company measures its success in terms of “engagement”—Silicon Valley-ese for how long people use an app and how intensely they interact with it—which helps convince marketers that users will pay attention to their ads. That means that when people retweet and like posts, Twitter benefits. Twitter super-users like Musk—the ones who reliably generate re-tweets, likes, and, in turn, revenue—are good for Twitter’s bottom line. It is telling that, in late July, Twitter’s CEO, Jack Dorsey, began a conference call with investors, meant to discuss the company’s quarterly earnings, by recounting a viral tweet by Serena Williams.