The possibility was one of a number of ideas that have been revealed in a new book about the history of Facebook and Mr Zuckerberg’s ascent to being one of the most powerful people in the world.
That book, written by author Steven Levy and some of which has been published in Wired, includes information taken from one of Mr Zuckerberg’s journals, written in 2006 as he was considering ways to make the early Facebook grow.
One of those was the dark profiles, which would be used for people who had either chosen not to join Facebook or had not got around to it yet.
People would create them for their friends, by entering their name and email address, the journals reveal. It would then be set up and let other people add information about the person to that page, like a Wikipedia article for anyone not on Facebook.
In the journal, which he referred to as the “Book of Change”, Mr Zuckerberg suggested it would be a good way of encouraging people to sign up. They could be alerted to facts people were writing about them and then be provoked into joining up, he suggested.
The Facebook boss was aware that the idea could be “creepy” and could stir up privacy concerns, he noted. But that might be assuaged with suggestions such as keeping them from appearing on search engines.
It is not clear how far Mr Zuckerberg’s idea did get, with Levy writing that some staff appeared to have worked on a version of it. It did not arrive in the form suggested in the journal.
As Facebook grew, it was suggested that the company was in fact creating separate hidden profiles for people who don’t use the site, so that they could collect up information for advertising even if people hadn’t actually created an account.
Mr Zuckerberg was asked about those suggestions in 2018, when he was faced with questions from US politicians. After those hearings, the company confirmed that it did track non-users, which it claimed to do for security reasons as well as ad tracking.
Facebook did not respond to a request for comment about the “dark profiles”.