It is usually low quality, mass market devices that are to blame. And, too often, devices that have been 'hacked' by the user to 'improve' the experience.
Recent reports had a pair of headphones 'explode' and seriously burn a passenger. Likely not hacked but could be the quality.
Unhacked ecigs are no more dangerous than other cheap devices. Ecigs are also a useful tool to assist addicts come clean. I doubt, however, that bubblegum flavours do anything other than encourage children to move money from their wallets to the wallets of legal drug pushers.