Viacom accused the video-sharing website of illegally taking Viacom's copyrighted works without proper authorisation.
Viacom said it will prove that 63,000 of its copyrighted videos, including clips from The Daily Show With Jon Stewart, South Park and MTV Unplugged, were posted on YouTube illegally. "Fostering and countenancing this piracy were central to YouTube's economic business model," Viacom charged.
In response, YouTube on its blog said that "YouTube and sites like it will cease to exist in their current form if Viacom and others have their way in their lawsuits against YouTube."
The popular video-sharing site said it will quote the safe-harbour provision of the federal Digital Millennium Copyright Act to defend itself. The Act states that a service provider is not liable for infringement if it removes material from its site when notified by the copyright owner.
YouTube will also argue that the law protects it "against claims arising from material uploaded to their systems by users," Andrew Schapiro, an attorney for YouTube, said in a letter to the court.