Zuckerberg, 23, stands accused of ripping off three former Harvard students, who claim they came up with the idea for Facebook and recruited Zuckerberg to work on it.
Cameron Winklevoss, his twin brother Tyler, and Divya Narendra claim that they employed Zuckerberg as a programmer in November 2003, but he went on to freeze them out of their own idea.
They allege that Zuckerberg stole the idea, source code and business plan, launching the concept as Facebook in February 2004.
The Winklevosses and Narendra will ask for total control of Facebook and its assets, plus damages, which could total $1bn. Facebook is now being given a pricetag of up to $10bn.
The suit alleges copyright infringement, stealing trade secrets, fraud and breach of contract. Zuckerberg has filed a counter suit of defamation.
The claimants have since launched , a similar social networking site that has not achieved the success of its counterpart.
Zuckerberg has already turned down a £1bn offer for Facebook from Yahoo! last year, and the site is currently attracting 150,000 new members a day.
Last week Facebook made its first acquisition with the purchase of Paraky.
.jpg)
.jpg)