The thin crusts and the hot gases are dangerous, but at least there is some indication of where they are! I think that really dangerous situation in Hawaii has been the unstable "benches" that are created when the lava flows reach the ocean. They can collapse without any warning. I believe there were some fatalities earlier this year or last year when this happened.
Yes, we saw warnings and heard stories of steam and collapsings, so we stayed very far from the edge. Plus it's such a darn long walk to begin with, then there's the sun, the heat radiating from the black rock, the open vent we saw (which, despite the 50+ ft. distance still radiated heat like an open oven in front of you). We were all hot and very thirsty when we got back, even though we carried water with us, but it was worth it!