It either auto fired uncontrolled or battery overheated. I'm thinking the first one. My Nemi once autofired when I put it down and luckily realized just in time and it was so hot I could barely touch it. After that it never happened again. Probably user moronity (that's my own word for user error/stupidity...hehehe)
Im honest when i say accidents do happen but i mean really. I get angry at articles like that as cars, booze and even your razor is a bigger health risk than an ecig. The man is trying to scare people with articles like that. I think you have a bigger chance at being hit by lightning whilst riding a shark thru a sea of cobras before an ecig blows like a grenade. Yes safety is always an issue as i too have had an auto fire accident but that just made me more carefull. Check locking rings and if a battery looks dodge dont use it. It just the way.