Mike, I do agree whole-heartedly with you on this point. I was speaking tongue in cheek so to say, being a S**t disturber.
I have often seen the same scenario over this side of the pond. Typically I believe that the poor fellow often taken by this is the newbie collector or the guy who just wants an Army Jeep and who could really care less about provinance.
This is especially rampant in the old muscle car hobby in Canada and the US.
With the prices being commanded on old vehicles there is plenty of room for fakes and very lucrative business opportunity.
Personally, I have always photographed my restoration work through progression as well as kept detailed documentation and receipts for parts and services. At least in this way I can show a buyer to the best of my ability and honesty when, where, how and why things were done. It puts all the cards on the table.
