The volatile stock market has claimed a new victim: Jack Dorsey's billionaire status.

Dorsey, the tech CEO multi-tasker who runs both Square and Twitter, saw his net worth fall below $1 billion on Wednesday as shares in both of his companies collapsed amid a broader market downturn, according to an estimate of his wealth from Forbes.

The founder's paper wealth, once estimated by Forbes to be more than $2 billion before Square went public, was down to $944 million on Wednesday morning.

Twitter, the social network beloved by 300 million people yet struggling to woo the rest of humanity, first fell below its $26 IPO price in August on concerns about its ability to reignite user growth (and having a part-time CEO). In the first weeks of this year, the stock has been hammered as the company throws "desperate" ideas at the wall (140 characters not enough? Have 10,000!) and investors flee to safer bets.

Square, the payments service Dorsey launched in between his first and second go-arounds at Twitter CEO, fell below its IPO price of $9 a share on Wednesday for the first time. Like Twitter, Square is not yet consistently profitable, faces strong competition including Apple, Google and Samsung and shares a CEO with, well, Twitter.

Investors are not amused.

TWTR data by YCharts

Twitter is now on the cusp of seeing its market value fall below the $10 billion mark, barely half the amount Facebook agreed to pay to buy messaging service WhatsApp two years ago. That will only increase the chatter about Twitter being an acquisition target.

"Topic of M&A becoming more prevalent in investors' minds. Potential acquirers could include large tech and media co's" - @bpeck, on $TWTR — Carl Quintanilla (@carlquintanilla) January 20, 2016

Square, meanwhile, is now worth less than $3 billion on the public markets, or less than half what it was said to be worth on the private markets a little more than a year ago. Its decline, paired with the decline of other newly public tech companies like Etsy, Box and Match, could serve as a cautionary tale for the many billion-dollar startups eying a public offering later this year.

It's not hip to be $SQ. I'll show myself out. — Chris Ciaccia (@Chris_Ciaccia) January 20, 2016

Square now below IPO price. 2 for 2 $SQ $TWTR — Ivan the K™ ️ (@IvanTheK) January 20, 2016

For Dorsey, however, it's more personal than that.

Dorsey has long groomed himself to be in the same elite group as Steve Jobs and Elon Musk, who each ran two companies at the same time — never mind that both men hated their lives while doing so.

Now, Dorsey is discovering the downside of that arrangement first-hand: having to watch, and be responsible for, two companies as they crash and burn at the same time.