This just in today - Nikon files a patent infringement lawsuit in Japan against Sigma over lenses with VR:
"Nikon's lawsuit seeks an injunction against Sigma's manufacture and sale of infringing interchangeable lenses with vibration reduction for single lens reflex cameras, along with damages for past infringement.
Although Nikon attempted to resolve Sigma's patent infringement through negotiation, a non-adversarial resolution could not be reached. Consequently, Nikon concluded that filing a lawsuit was the only way it could protect its intellectual property."
Update: according to Reuters, Nikon is looking for a compensation of 12.6 billion yen (around 150 million dollars).