> Is seems fairly obvious to me that inhaling vegetable glycerin and nicotine does not cause any harm.
Why is that obvious? Lungs evolved to absorb oxygen not vegetable glycerin or propylene glycol. In fact there is some evidence that it may be harmful to protective cells in the lung walls, potentially increasing the risk of lung inflammation[1]. Obviously we'll have to wait 30 years to know of any long-term effects, but maybe common sense would be a better life decision if you don't want to be a test subject.
I would also suggest that there is a risk of cheap e-cigarettes causing even more serious harm because they might have contaminants in the fluid being inhaled.