Tesla's stock could fall much further

The recent decline in Tesla stock, possibly caused by worries about Musk's successful bid for Twitter, has raised concerns that he barely has the liquidity to raise the $21 billion he needs to provide in cash to pay for his new platform.

By the numbers: If you exclude stock that Musk has pledged to secure loans, the value of his freely-sellable Tesla shares is only about $11 billion. In order to find the extra $10 billion, he might have to exercise some of his stock options. That's expensive, since he'd need to pay income tax, rather than lower long-term capital gains tax, on such sales.

• What goes down can go down much further: Tesla stock is about 33% below its all-time high. Yet Facebook has performed much worse than that, while rival electric carmaker Rivian is down more than 80%.

A continued decline in Tesla shares could cause margin calls and a lot of forced selling by Musk, which in turn would tend to drive the stock lower still.

• Lauren Silva Laughlin and Gina Chon of Reuters Breakingviews have already gone so far as to predict that Musk will never own Twitter.

The bottom line: Musk is that rarest of billionaires: one who's always keen to put his wealth to use, rather than just watching it rise, or giving it away.

• A $44 billion purchase, however — almost certainly the largest amount of money ever spent by a single human on anything — might be too large a bite, even by Musk's standards.