But lets say you have a US iPhone and you want to changed it for a UK iPhone for any reason - you could go buy one from O2 bring it home and swap it over.
Of course your US iPhone would have to be in good condition still and you would have to de-activate it first.
I do not think that 02 and Carphone Warehouse are going to be turning on the iPhone and checking the IMEI numbers and firmware versions! They will just check the box and see its looks new and give you a refund!
Of course the next poor sod who goes and buys the one you return will not be happy and they can track you as your paying by card but I imagine even if that happens they will just give the guy who had your old phone a new one and return the other one to Apple.
Not honest and maybe not worthit but if you did REALLY brick your iPhone then it would work!