From the Guardian...
"Most embarrassingly for Viacom, court documents revealed in in March that at the same time that it was suing Google and YouTube, Viacom was itself uploading its content in secret and trying to make it look stolen - so that people would be more interested in it.
One excerpt from the documents filed by YouTube was particularly notable for the embarrassment caused: "Viacom's efforts to disguise its promotional use of YouTube worked so well that even its own employees could not keep track of everything it was posting or leaving up on the site. As a result, on countless occasions Viacom demanded the removal of clips that it had uploaded to YouTube, only to return later to sheepishly ask for their reinstatement. In fact, some of the very clips that Viacom is suing us over were actually uploaded by Viacom itself."
So Viacom were being pretty dodgy about IP in the first place, then complaining!