I've been reading articles and forum threads on MacRumors forums for a while, but I only recently registered.
After reading this thread, I'm inclined to believe the OP. Some of the details are not filled in completely, but with the pictures and the copy of the apple store work order, it looks like this is a genuine incident.
I don't think the OP's math quite adds up to 4000 of fires or what ever you want to call them a year, especially because the iPhone isn't as popular all around the world as it is in the North America or Europe. If there were really 4000 a year, we would hear a lot more about it.
This seems to be pretty isolated to a few cases. I think that Apple makes quality products, and as we see by the warranty replacement in this case, they stand behind the products and will uphold the warranty.
Just my two cents.