I don't think many people use protected cells in vape devices anymore. Samsung, LG, and Sony all have high quality IMR cells. Why people choose to cheap out on batteries in a device they put in there mouth is beyond me.
As a guy who vapes (to quit smoking, not to be a douche) yeah, this is due to people either building their own coils incorrectly, poor quality batteries (which is stupid because good batteries only cost like 15 bucks) and using unregulated 'mods' (the battery holders). Also, some people also cheap out on the battery chargers, which dont protect them from overcharging. Lastly, even good quality batteries have their skins rip off over time, which can easily lead to shortouts. Anyone who vapes (and I was under the vise that a lot of V-DUB guys do) be sure to check into all of the above so you don't burn your cool hipster beards off!