I have always wondered why Windows treats a USB device plugged into one port as a brand new usb device when plugged into another port. My Mac never did this, or at least it was never apparent. However, the fact of the matter is, Windows makes it very obvious to you when you've added new hardware, even if that is a USB KeyChain drive or something. I'm not sure if that is a good thing or a bad thing.
At least I know that this is because the device does not have a serial number (Thanks Raymond for the explanation):
"In other words: Things suck because (1) things were already in bad shape—this would not have been a problem if the device had a proper serial number—and (2) once you're in this bad state, the alternative sucks more. The USB stack is just trying to make the best of a bad situation without making it any worse."
This can pretty much some up most of technology. Compatibility is king.