I think perhaps the site Anne referred to is in the UK? I can only say that I have been stung by bumblebees, on more than one occasion, when I inadvertently got too close to the nest without realizing they were there. One even chased me a few yards when I ran away, and stung my hand when it caught up to me. Needless to say I gave the nest locations a wide berth after that!
I found this on another (UK?) bee website:
"Bumblebees are reluctant to sting, and appear to do so only if they are mishandled or their nest is threatened. However I have heard recently that some species of bumblebees found in America (north and south) are more aggressive than European species. So always treat bumblebees with respect as there are some people who have an allergy to bee venom that can lead to death even after just a single sting if not treated promptly."
From:
http://www.bumblebee.org/bodyS...