Yeah, nasty stuff. There were warnings about it at WOC91 in Czechoslovakia, and I know at least one orienteer who had an unpleasant run-in with it in Canada. (Or it might have been the similar cow parsnip instead of giant hogweed.)
Nuke it from space. It's the only way to be sure.
For the amount of cow parsnip around southcentral Alaska (covers about 15% of my yard), I don't hear of people being burned by it often. Most people are aware of it and make a point not to touch it - not hard to avoid, and every touch doesn't burn - just the juicy ones. I've been told to not even burn the dried stems because its toxin can burn the lungs when inhaled. It deserves respect.