We had an 'incident' here at ISK where an AMM put OM15 into the engines but that is because this particular AMM is maybe a tad slow on the uptake (recruitment issue?).
You cannot legislate for stupidity but there are also plenty of times where HF comes into play.
As for the argument of 'throw the book at him', when was the last time a heavy landing which subsequently causes an untold number of man hours wasted fixing the jet (and then lack of flying hours for other crews) or whoops I seem to have taxied the jet into a building ever resulted in 'lets throw the book at him'?
(I can give plenty of other 'incidents' from the flying side from the past 21 years if you so desire)
Whats good for the goose...........................