Dear Duncan,
In message 1814106598.1047276.1510787951141@mail.yahoo.com you wrote:
Many board manufacturers "assign" this unique MAC address by printing it on a sticker and sticking that on the board somewhere. It's pretty darn hard to read a printed sticker in software, so we have to revert to solutions that actually work.
Such solutions usually include a barcode reader attached to some PC which is used when you commission the board. And yes, in this case it is mandatory that the MAC address(es) stored in the environment (which gets initialized as part of the aforementioned commissioning procedure) takes precedence over any MAC address(es) that might be stored somewhere in the hardware.
In the "clever things" department, protocols like IPv6 merrily broadcast your MAC address across gateways on the big bad internet, so if you value your privacy, you'll appreciate the possibility to change your MAC address at will.
Right, this is another of a list of reasons why changing the MAC address makes a lot of sense.
Best regards,
Wolfgang Denk