Not so sure, Martin did post a "Like" on my OP, so he has taken part!
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If I can find the thread and specific post again, I'll post the link, but I did read a few weeks back on the German pedelec forum, that Bosch intended to clamp down on Bosch authorised dealers that are selling dongles, or more specifically, look closer at warranty claims made by those dealers that are known to be selling dongles.
If Yamaha were to follow suit, then it would seem to be a very daft dealer that is happy to risk loosing a franchise and possibly a down turn in business, through biting the hand that feeds it, the bike manufacturer.
It would be interesting to hear how Martin proposes to get around the issue of opening a warranty claim, in the possibly unlikely event of a motor failure.
If it were me, I'd be starting to get a bit twitchy.