Speaking for myself, my personal list of chasing dangers is as follows:
1.) Car Accident - Other drivers/chasers, head-on with a semi on a two-lane highway, animals in the roadway (like big ones...cows, horses, pigs, sheep, deer...close calls with most of these...hey, I live in Oklahoma), hydroplaning, falling asleep driving home after a chase, etc.
2.) Lightning - Can't see it coming and no warning. Just "ZAP!!!!" and the lights go out. Too many close calls.
3.) Flash Flooding - Especially at night. Sometimes while driving down a blacktop, you can't really see it until it's too late. Also gets back to the hydroplaning accident thing.
4.) Gorilla Hail - I have been fortunate to not get caught in softballs or larger thus far. The sound that baseballs make when dropping from the sky is truly something to behold, I can only imagine what a softball shower would sound like. Makes my head and my car hurt thinking about it.
5.) Public/Chaser Convergence Disaster - Either on a highway anywhere near an overpass when people start plugging up the roadway to park underneath it, or being grouped together in a chaser traffic jam with few road options and getting into a bad situation and getting munched by Mother Nature.
You'll notice tornadoes aren't on the list. I, like many other chasers on here, am not concerned with the safety factor presented by tornadoes. I do not possess the need to get really up-close and personal with a large and violent tornado. I am perfectly content sitting back a little further and getting the tornado and some good structure to boot. Keep your head on a swivel and always keep checking your back to see if anything may be sneaking up on you and keep your distance and you'll be fine. My opinion.