First off, I'm just posting for the sake of sharing information. I really have no intention of causing anybody any trouble.
With regards to 2nd-hand sales of equipment with "unfilled warranty", take note that some particular companies do not insist on an official receipt (with purchase date), but SOME DO. I found this out for myself when I sent in a camera for repair. It was a 2nd-hand piece, unfilled warranty. As I did not know exactly how old the camera was, I fudged a purchase date on the warranty card (I tried to make it as convincing as possible - 10 months prior). I had no official receipt, but it didn't matter to them because they tracked where and when the camera was purchased and we found out it that the warranty had already expired by 2 months.
Some other companies do not require official receipts, and are less fussy about how old you say your camera is, but they also do often have a clause that gives them the right to reject your warranty w/o reason.
In short, read all the terms and conditions on your warranty certificate!