The Nikon D3 buffer upgrade was introduced back in July of 2008. Today Nikon announced that the service will be discontinued on July 20th, 2011. If you own a D3, you have another month to perform the upgrade:
"Please be aware that the D3 Buffer Memory Expansion service introduced as a payable upgrade option to Nikon D3 owners on 30th July 2008, is now being discontinued. This upgrade option will end on 20th July 2011 and not be available after this date."