Having been to the lava flows in Hawaii, it was scary (and extremely hot) enough just to be 50ft. from a glowing red crack in the hardened surface and not know how thick (or thin) the crust was we were standing on. We, and many many other tourists, had ventured past the recommended "safe" zones. As a tourist I would never get that close to an active flow - way too hot and unpredictable.
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.