Updated below to include comment from Google’s general counsel. Google, which sometimes refers reporters to YouTube PR for comment, responded to Viacom copyright infringement lawsuit for both via a Google spokesman:
“We are confident that YouTube has respected the legal rights of copyright holders and believe the courts will agree. YouTube is great for users and offers real opportunities to rights holders: the opportunity to interact with users; to promote their content to a young and growing audience; and to tap into the online advertising market.  We will certainly not let this suit become a distraction to the continuing growth and strong performance of YouTube and its ability to attract more users, more traffic and build a stronger community.”
It could be argued that the possibility for distraction lies partly with Google for continuing YouTube’s initial strategy of connecting license deals with copyright protection after the acquisition and for not being more clear now about how it could work for non-licensees. That might not have stopped this infringement suit—or others—but it would have removed one major sticking point and given Google and YouTube some higher ground.
Update: Another email from Google adds that the company has not yet received the suit.
Update II: Google’s been busy as you can imagine. An updated response brings General Counsel Kent Walker’s take—as in, take that, Viacom: ”YouTube has become even more popular since we took down Viacom material. We think that’s a testament to the draw of the user-generated content on YouTube.  We’ve been very successful forging thousands of successful partnerships with content owners—like Warner Music, Sony/BMG, Universal Music, BBC, and the NBA—interested in finding new audiences for their programming.  These partnerships offer the YouTube community access to some of the best content in the world, ranging from entertainment and sports to politics and news.  And we’re only getting started.”