Musk suggested Tesla would hit 500,000, and the SEC alleged contempt of court after an earlier ruling about dubious Musk tweets last August (which sent Tesla's share price bouncing around like - in the immortal words of Jack Lemmon - "Jello on springs").
The SEC didn't like the latest tweet for two reasons: first, the figure seems suspect (Musk later hedged down); but more importantly, it broke an agreement that all his tweets would be vetted before he hit the send button.
Elliot Lutzker, formerly of the SEC's enforcement division, told me yesterday that Musk is "incorrigible" and that "he shouldn't be running a public company."
Lutzker foresees a stiff fine and possibly banning Musk from being even an executive at Tesla, forcing him to become an external consultant to his own business.
"The SEC is not looking to put him out of business. But he's going to have to abide by the rules," he said.
And the SEC has a pretty big stick to keep him in line - access to the markets and public funds, without which Tesla will go out of business.
"Musk may think he's bigger than the SEC," said Lutzker. "But he isn't. They have the leverage. He doesn't."
That's as maybe. Yet while Musk's behaviour drives the SEC, shareholders, bondholders and lawyers up the wall (Dane Butswinkas, Tesla's general counsel, left a few days ago after only two months in the job), the latest kerfuffle will suit him perfectly.
For when you are trying to bust into a saturated marketplace filled with dominant, established brands, you cannot play by their rules. You have to create an extraordinary sense of hype around your product.
You have to create a magnetic storm of press coverage (like this) so that your every move makes vast headlines and does your advertising for you. You need to be not just professionally but also personally disruptive.
Of course you use Twitter as a dream comms tool. You might even be tempted to use it to bend the truth. See also Donald Trump.
If Musk was to calm down, obey the rules and play nice, Tesla would fail. That, not the SEC contempt filing, is the real risk he faces.
His company needs to be on everyone's lips. He and his behaviour is why your technophobic parents have heard about Tesla even though they have probably never seen one of its cars. That's remarkable.
And it is a result of the fact that while he hates addressing boring questions from investors on earnings calls, he loves telling Popular Mechanics - as he does in his latest interview - about what man's colony on Earth will look like.
While the SEC rants, Elon is actually talking about how we will feed ourselves on the Red Planet (answer: hydroponics. "You don't have to worry about excessive ultraviolet radiation or a solar storm or something like that. Really pretty straightforward.")
The man is just fantastic value. His imagination is gold. The SEC talks about executive bans, he talks about transforming Mars so that it develops at atmosphere "and you can walk around without a suit" - a process known as terraforming.
He dismisses sceptics: "Of course you can terraform Mars. Why would they think you can't? You totally can."
His frustration with the naysayers is evident. Of course, when disruptive companies reach a certain size they become the establishment and their disruptive founders can move on. Look at Microsoft and Apple.
But Tesla is not there yet. Not by a long chalk. So the time is not yet here for Musk to rein himself in, even if he could. He doesn't just want to copy the car industry. He wants the car industry to copy him.
That is a transformation so large that it extends far beyond automobiles into the political and social realm of how we human beings want to live our lives. It is trite to say, but Musk is not a manufacturer or a businessman, he is a revolutionary. True to the genre he combines brilliance with instability.
He also has the required vision, capability and charisma. Such talents frequently prove as dangerous as they do beneficial. But they are rare as hens' teeth. And if your commercial vision really does involve changing this world, or indeed another world, you need nothing less.
