Upload & Sell: Off
Having the warranty card ONLY matters if you also have their original sales receipt from where the camera was purchased.
A serial # tells you a few things, provided that you have an index of Nikon Serial #s:
-When the camera/lens was made. Serial #s are sequential, so if you know what the starting production date was, and how many were produced over a set length of time, you can get an approximate "birthday" for your camera or lens. For example (not real serial #s, just an example), a 50mm f/1.4 AFS with a serial # of 0000001 is produced in October 2008. If Nikon makes a steady 3000/month, then a lens with serial #0012000 came off the lines in January 2009.
-Where the camera/lens came from, and where the product was licensed for sale.
You can call up Nikon USA and have them run a serial # for you on their toll free, 7 day a week, 8 AM- 2 AM EST service line. 1-800-645-6689. They can verify that a Nikon product is a USA licensed product, or a "gray market" import.
If you can get the original sales receipt, I'd get the one with the blank warranty card!