Setting light to a derailleur
Well I thought we needed an answer to this, so I just phoned the shop. He's a nice fellow (as you can tell from the vid) and said that his mechanic is convinced that this method works to free-up seized and corroded mechs. Apparently dousing it in something like GT85 and lighting it for a very short time boils in the lube, and works. 

I assume that the combination of a penetrating lube, some heat, and vapour would achieve this as a last resort for badly seized metal components. I've done something similar on bearings when trying to get them out of BMX cups in the past.