I have a Tornado and an eGo, I have experienced a sticking battery button and a stuck on battery with these devices.
First, the Tornado battery got stuck on and stayed stuck on (running continuously) with a LRA on it after I took a few hits off of it. The battery button was not stuck in the on position (pushed down), the button was in the off position (raised up) but the battery was still discharging power. Next thing, I hear a hissing coming from my LRA, getting louder and louder each fraction of a second, I removed the cartridge... BOOM! It blew up in my face, a few small drops of hot liquid shot out of it; wasn't cool
Second, with the eGo, I pulled it out of my pocket to take a vape and the battery button was stuck on (pushed down), I pushed it a few times and it was still stuck. So I then began bashing it with a katana and ended up slicing my eGo into tiny little pieces during my outburst of outrageous insanity. No I'm just kidding. But I did have to smack the eGo on my hand to get the battery to turn off. I'm not sure how long the battery was running... anywhere from a couple seconds to a few minutes... Luckily I had a cartomizer on this time, it seemed as if the device suffered no damage at all, it worked just as well as before.