The stock market value of Snap, owner of the Snapchat messaging app, fell $1.5bn after reality TV star Kylie Jenner said she no longer used it.
Ms Jenner told her 24.5 million Twitter followers: "sooo does anyone else not open Snapchat anymore?"
She was adding her powerful social media voice to the growing criticism of Snapchat's re-design.
Snap boss Evan Spiegel had something to soften the blow, though, with news his total pay was a huge $600m last year.
Shares in Snap fell more than 8.4% to $17.8, falling back close to the $17 price at which the shares were listed when the company floated on Wall Street.
The disappearing messaging app was re-designed in November. But many users criticised the change, and one million people signed a petition.
Ms Jenner, the half-sister of celebrity Kim Kardashian, tweeted: "sooo does anyone else not open Snapchat anymore? Or is it just me… ugh this is so sad."
She did, though, later tweet a follow-up: "still love you tho snap… my first love".
Snapchat has rejected complaints about the re-design, with Mr Spiegel saying earlier this month that users just need time to get used to it.
The criticism from Ms Jenner was followed by news that Mr Spiegel received $637.8m as total compensation last year after the company went public.
It is thought to be the third-highest annual payout ever received by a company's chief executive, although the compensation package was heavily boosted by the award of shares in the company. His salary for 2017 was $98,078
The package trails the 2007 and 2008 compensation packages for Daniel Och, head of hedge fund Och-Ziff Capital Management.
He received an annual compensation of $918.9m in 2007 and $1.19bn in 2008.