Facebook is pressing ahead with its plans for an e-currency.
Backers of the Libra digital coin met Monday (October 14) in Geneva.
By day's end they were one fewer in number.
Online travel company Booking Holding has pulled out.
It's the owner of sites including Booking.com and Priceline.
The departure follows earlier exits by PayPal, Mastercard and Visa.
Without them consumers may find it hard to turn their money into Libra.
All were spooked by warnings from regulators in the U.S. and Europe.
They say Libra could upset financial markets, undermine users' privacy, and aid money laundering.
The Libra Association is undaunted though.
It called the latest defection "a correction, not a setback".
Prominent firms including Uber, Lyft and Vodafone remain part of the team.
The Geneva meeting also named five members to a Libra board.
However a spokesman said that the regulatory worries could yet delay the coin's launch.