That's not what is alleged...
According to http://www.theregister.co.uk/2010/07/21/ceglia_facebook/ , Zuckerberg signed a contract, in which he got a $1,000 investment for a website "designed to offer the students of Harvard university access to a wesite [sic] similar to a live functioning yearbook with the working title of 'The Face Book'.
According to the previous article : "The contract, due for completion on 1 January 2004, granted Ceglia a 50 per cent stake. For every day past the due date he would be granted a further one per cent, leading to his 84 per cent ownership claim."
This really could be epic. If he did sign that contract, I can't see how legally he could be allowed to weasel out of it.