Ethernet MAC address spoofing

[Matteo Vadagnini <tovaldez () katamail com>]

Hi to everyone.
As you know many OS permit to modify Ethernet MAC address "on the fly"
(Unix most of all through "ifconfig", but also Windows with third party
software).
My asks are:
-Where this modified address is exactly stored? (in the kernel memory 
area?)
-Is it possible to change the MAC address of a wireless NIC, and which
security issues introduce this possibility?

Thanks for the answers to my curiosity.

references to documentation is well appreciated.

Mat