Logic, common sense and sound business practice to score repeat and loyal customers would fit both to cover all bases 
or hang all that, fit both just so the CEO and staff at Weller can sleep better
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FWIW I don't agree DJ should cop the rap of 'user error' on a unit made by a company that flogs it's wares to a 120 volt @ 60 hz nation that also has a 240 volt supply.
DJ plugged it in and the unit smoked because the manufacturer FAILED to deploy a cheap fusing device to prevent an input voltage mishap,
and no real obvious appropriate caution labeling
Had DJ tried to run the unit from a 120 volt ugly square wave inverter, some aviation 400hz thingie or a dimmer buzz adapter to control the temperature, and the unit smoked or popped a lamination after a time,
well, that's definitely a strong case for 'user error'
Who says it always is due to 'user error' ??
A fault with the power delivery system, say a missing neutral or insufficent grounding, and your mains 120V system could face 240V across L-N.
I have personally seen an extremly expensive projecter burn and die due to a such an error. The neutral connection at the convention center was not tightened well enough, eventually causing a thermal runaway situation before it disconnected/opened. Result: 240V mains was suddenly 380V, as this was the only phase-neutral drawing large amounts of power at the time. Fortunately a replacement could be fetched in time, though it was not nearly as good.
Some people hope/wish for the best, and if they are assured nothing will happen - nothing should, right?
Famous last words, I thought ... (and <gulp> I was wrong)
Difference in culture and opinion, what is common sence and so on. I totally understand why some people are so paranoid, it's usually those who has already been burned in the past :-)