To put this into perspective:
"Each year, about 4.5 million Americans visit their doctor’s office or the emergency room because of
adverse prescription drug side effects. A startling 2 million other patients who are already hospitalized suffer the ill effects of prescription medications annually, and this when they should be under the watchful eye of medical professionals.
All kinds of medications, from those that are considered “all natural” to those that are chemically produced in a laboratory, carry some sort of aftereffect. Even though prescription drugs are supposed to undergo stringent testing and clinical trials,
federal drug regulators allow a level of side effects. In addition, most side effects vary from person to person, depending on the dosage, the patient’s disease, age, weight, gender, ethnicity and overall health."
http://www.drugwatch.com/side-effects/
So if you've ever bothered to 'read the manual' on any prescription drugs you have taken, there will be a list of side effects that give a percentage of people that experienced a wide range. That percentage is usually miniscule to the number of people who have taken the drug.
Here's FEMA's take on lithium batteries used in ecigarettes:
"
What we found
Media reports of 25 separate incidents in the U.S. dating from 2009 to the present (Oct 2014) were found during an Internet search. This list is not thought to be all-inclusive since it is likely that there were incidents that were not reported to the fire department and/or reported in the media. The media reports were reviewed, and key information was extracted and summarized."
https://www.usfa.fema.gov/downloads/pdf/publications/electronic_cigarettes.pdf
And a graph that accompanies the study:
First not only do your batteries have some level of protection - all have charge protection, many now have short protection, and the chargers used have those protections and sometimes reverse polarity protection as well - as do some mods. While the probability of the charge protection in BOTH devices (batt AND charger) going out while charging, is quite low, the possibility still exists.
This is why I always unplug any device charging when I leave the house or go to sleep. In over six years of constant daily vaping - and recharging, I've never had a fire, meltdown, explosion. I've had about 3 or 4 times when I've 'checked' (touched) batteries charging where they were hotter than what was normal. I took them off the charger, turned them off (if that was possible) and threw them and the charger away.
When one of our posters has an 'incident' almost everyone hears about it. If you go to any cell phone forum, flashlight forum, radio controlled toy forum, laptop forum, etc. the same will happen. And if the media gets wind of it - it will be on every station. But for the trillions of mAh's of all the batteries, the number of incidents - some of which not pretty - is still under the level of the side effects of drugs which kill over 100,000 people each year.
I hope that accomplishes task of my first sentence above :- )