A hardware hacker called X-Shadow has found a way to flash any ROM, including an unlocked ROM, to the Nokia Lumia 800.
The method is however not for the faint of heart, requiring disassembly and access to the test point connectors on the circuit board, and the use of a Advance Box turbo flasher.
The method is not helpful for the everyday user, but one can imagine a hardware hacker in a major city easily setting up business unlocking Nokia Lumias.
Read more at XDA-Developers here.
Thanks Heathcliff74 for the tip.