Mark Zuckerberg lost $29 billion in net worth on Thursday as Meta Platforms' stock marked a record one-day plunge, while fellow billionaire Jeff Bezos was set to add $20bn to his fortune after Amazon's blockbuster earnings.
Meta's stock fell 26 per cent, erasing more than $200bn in the biggest ever single-day market value wipeout for a US company. That pulled down founder and chief executive Mr Zuckerberg's net worth to $85bn, according to Forbes.
Mr Zuckerberg owns about 12.8 per cent of the technology behemoth formerly known as Facebook.
The decline in the fortune of Mr Musk, the world's richest person, came after he polled Twitter users on whether he should sell 10 per cent of his stake in the electric car maker. Tesla shares have yet to recover from the resulting sell-off.
Meta reported no growth in monthly Facebook users in the fourth quarter relative to the previous period.
For Meta, the disappointing earnings add to its challenges. It is in the middle of a number of regulatory fights and also looking to justify its strategic shift to bet on an immersive internet known as the metaverse.
Meanwhile, other platforms such as TikTok and YouTube are gaining ground with younger users.
Mr Bezos, the founder and chairman of e-commerce retailer Amazon, owns about 9.9 per cent of the company, according to Refinitiv data. He is also the world's third richest man, according to Forbes.
Amazon's holiday-quarter profit surged, thanks to its investments in electric vehicle company Rivian. The company said it would raise the annual prices of Prime subscriptions in the US, sending its shares up 15 per cent in extended trading and readying it for its biggest percentage gain since October 2009 on Friday.
Mr Bezos's net worth rose 57 per cent to $177bn in 2021 from a year earlier, according to Forbes, largely from Amazon's boom during the coronavirus pandemic when people were highly dependent on online shopping.
Trading in technology stocks remains volatile as investors struggle to price in the impact of high inflation and an expected rise in interest rates.
Meta shares could very well recover sooner rather than later, with the hit to Mr Zuckerberg's wealth staying on paper.
Mr Zuckerberg sold $4.47bn worth of Meta shares last year, before 2021's technology retreat. The sales were carried out as part of a pre-set 10b5-1 trading plan, which executives use to allay concerns about insider trading.