I disagree with the statement that “I don't mean to dismiss the BE case as being trivial, it's not. Fortunately at the concentrations offered the net result is a toxic, not lethal.”
According to Wikipedia Nicotine - Wikipedia, the free encyclopedia a lethal dose can be 40-60mg for non smokers and 80-120mg for smokers… Depending on the weight of the person. I’m sure If you ingest it, its less lethal because of the stomach acid counter acting the base in the nicotine, and less gets in your bleed stream. And yes if you vape 40-60mg you will get sick before you get to the lethal doses.
But what if your DIY’er making liquid, and you spill some on you. If you soak just 0.5ml of 270mg nic into your skin, that IS lethal. Add to that the fumes you will get while working with it. And if you THINK your are working with 50-100mg, your less likely to be as causios than if you KNEW you were working with 270mg. I personally only work with <50mg nic when doing DYI, but I did work with a higher mg batch by mistake a while ago, and started to feel the effects just by the fumes cutting it down.
Just a small refinement - I think ingestion would be the worst case because a lot of it would be absorbed before reaching the stomach (and i would guess faster than on the skin) and the throat swelling alone might be sufficiently serious to cause death.