Only when something silly has been done like dead shorting it for a while. That said, I did accidentally do this. The cell leaked and was destroyed but there was no smoke or flames. Try hooking it up to a car battery charger set to 5 amps and you'll get it to blow - but that would likely make an NiMH leak violently at best too. You can make NiMH cells go bang - you just have to work hard to do it.
Your chance of being killed by a dead fish dropped by a seagull while in the Sahara Desert is considerably higher. Single cell lights are safe enough. Most exciting stuff with lithium cells is when they are being overcharged or charged at too high a current. I would toss any lithium cell that was below 2.5V on standing for an hour or two. It will probably be safe, but it will have a small fraction of its original capacity. Anything that had been charged above 4.35V I would be happy to use but would not attempt ever to recharge it again. Some of the newer very high capacity 18650 cells are designed to be charged to this voltage - the Chinese stuff most of us buy emphatically is not.
The cells are cheap enough and my flesh isn't. In general to give the cell a chance to live beyond a few cycles it is best to keep discharge rates below twice the capacity unless the cell is specially designed for high discharge rates like the AW IMR cells or Sony's equivalent. So for a 2400mAh 18650 I'd not want to discharge it at more than 4.5-5A. I have had an unprotected 18650 provide 9A until flat, and recharged it several times. It didn't last a year but it didn't do anything exciting either - just stopped working.
The risk is pretty low, but not zero. I've never really given it a thought but I do pay attention to what voltage they are coming off the charger. Above 4.35V Bad Things are likely to happen.
All the dead lithium ion cells I've had have failed gracefully - they just wouldn't hold a charge any more. One of them actually showed a small negative voltage - I most certainly did not try to recharge that one.
For fun, we once connected a dead RCR123 across a 200A welder then turned it on. That stuffed something like three kilowatts into it.
Briefly.
Best to do this outdoors and I didn't think to bring a camera.
Doing that to almost any other battery would have the same result but wouldn't have hot hydrogen fluoride and burning lithium metal as a door prize.
Almost everyone gets away with using and abusing lithium ion cells with no harm to themselves - not that I am recommending this - all that happens is that the life of the cell is drastically shortened. I would check voltages as a matter of course in multi-cell lights.
At least when they came off the charger.
And maybe occasionally in between charges.
But then there is no light I own that I would not be prepared to throw as far as possible and then run if I thought the cells in it were doing Bad Things.