What fails on them?
It did work reasonably well, but if you failed to clean it and fully dry it out within 6 hours of using it, it would get an INSANE mildew smell.
Amazon of course didn't bother to do anything about the company when I tried to report them, and they seem to have disappeared/rebranded since then
My guess is water is getting trapped somewhere in the device's Chinesium crevices, or maybe they found a way to make plastic cheaper by making it susceptible to mold.
Technology Connections had a good video on the quality of humidifiers: https://www.youtube.com/watch?v=oHeehYYgl28
1. Electronically (ex: you can do this in your bedroom directly, or anywhere you need the warm-mist)
2. With safety measures (its still dangerous, but they minimize the amount of boiling water to minimize the possible harm. Better than an entire pot of boiling water, but still half-a-cup of boiling water can severely burn you still)
3. Probably as cheap as the pot you were using to boil water anyway. Warm mist humidifiers are like $35.
If you have an electric stove, boiling water will be less efficient than evaporating water and letting your heating system make up for the loss in sensible heat unless you have an electric furnace.