Viacom is suing YouTube (that is, they're suing Google's deep pockets) for copyright infringements posted on YouTube. This is an interesting legal case, because you'll find people saying it's obvious that the DMCA protects YouTube, and you'll find people saying its obvious that the DMCA (plus the Napster and Grokster cases) nails YouTube to the wall.
The conventional wisdom is that Viacom, by taking down all these pieces of their video shows, is killing off the best advertising vehicle in history. And more conventional wisdom says that Google and Viacom will settle, with Google giving up a ton of change.
I'd like to point out something I haven't heard yet about this case. Google's deep pockets mean it could contest this case in court, possibly dragging it out five years or more. And Viacom (and indeed the entire movie and TV industries) are taking a terrible risk if there's a real lawsuit: Google may challenge the estimated value of the copyright violations. I believe the current estimation (used by Viacom) is $750 per violation, it could even be higher. But there's no proof of any such estimate. In fact it may be hard to prove there are any damages at all, with the benefits of violations accruing to Viacom in the form of free advertising that boosts sales. Viacom will lose the war if a court case decides that yes, there were punishable violations, but that Google does not owe one cent to make the violations good.
I'd dearly like to see Google challenge the idea that copyright violations of video on the web cost the copyright owner anything.