There\'s other valid reasons also, such as when MAC addresses conflict, despite the fact that they\'re supposed to be globally unique (yes, I\'ve seen a batch with all the same MAC). Also, if you\'re on a wifi access point that you have legit access to, but have changed your card, it\'s sometimes easier to change your MAC than jump through the hoops of re-registering.
Anyway, to do it, you can either use the ifconfig command, or macchanger. Macchanger is available as a Debian ARM package, and does work on the Z. I think I had to manually untar and install it, but I\'m not sure anymore.
Or, even easier, you can use the following.
ifconfig eth0 hw ether DE:AD:BE:EF:00:00
substituting for the appropriate interface, and the desired MAC address, in hexadecimal.
Both ways of changing are software-based, and won\'t persist over a reboot or removal/insertion cycle. In other words, you aren\'t changing the hard-coded MAC, more like \"spoofing\" the MAC.
(For Windows users, there\'s a program called SMAC that will do the same thing.)