It is being sued by a patent-holding company acting on behalf of a dead Dutch programmer called Joannes Jozef Everardus van Der Meer.
Rembrandt Social Media said Facebook's success was based, in part, on using two of Mr Van Der Meer's patents without permission.
"We believe Rembrandt's patents represent an important foundation of social media as we know it, and we expect a judge and jury to reach the same conclusion based on the evidence," said lawyer Tom Melsheimer from legal firm Fish and Richardson, which represents the patent holder.
Facebook said it had no comment to make on the lawsuit or its claims."
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