I also do the ratcheting thing on occasion to get round a really tight corner, having had overlap on many big wheel bikes through my life, including my Dawes Windsor touring bike bought new circa 1981, which had 27x1 1/4" wheels and a 19" frame. If when turning at low speed my shoe touches the mudguard I instinctively turn the pedals back and take it from there.
If there is too much gradient to use the ratcheting technique, such as in the instance Mick F describes, it is time to get off and push it round, and this has only caused a problem a couple of times soon after adopting SPDs when unclipping speed was less than perfect and I started to topple over. Fortunately managed to get out just in time. Another use for ratcheting when I was a kid was for getting across a large puddle where momentum was not enough to carry you across and you wanted to avoid getting your trainers wet.
It is really no big deal for me personally, but I totally agree that it is potentially dangerous to a novice, or someone who has been fortunate enough to have not met it before, due to their height making it unlikely with most frames of the correct size for them. For that reason I think that legislation could probably do with being made more robust, at least for bikes other than road racing designs, and there possibly should be some sort of warning label and statutory giving of advice by the seller in the case of road bikes with tight clearance.