An influential tech evangelist has called at the TED 2018 conference for an overhaul of Facebook and Google's business models.
Jaron Lanier, who is often referred to as a "father of virtual reality", told the Vancouver event that the two firms should let users pay for their services as an alternative to relying on ads.
"These companies need to change," he said.
But on Tuesday, Facebook's chief suggested this would not be popular.
"A number of people suggest that we should offer a version where people can not have ads if they pay a monthly subscription, and certainly we consider ideas like that," Mark Zuckerberg told a panel of senators in Washington.
"But overall, I think that the ads experience is going to be the best one.
"I think in general, people like not having to pay for a service. A lot of people can't afford to pay for a service around the world," Mr Zuckerberg added.'Tragic mistake'
Mr Lanier was a frequent TED (Technology, Entertainment and Design) speaker during the 1980s.
But, he said, even then he had realised that "the technology we needed and loved could also be our undoing".
"We made a very particular mistake in the 90s when early digital culture had this lefty, socialist mission, which meant that everything on the internet must be available for free," he added.