Bumble bees are beneficial insects that pollinate plants and flowers. Their activity in gardens is desirable but It is best to not allow them to nest in areas where children and pets often go or play. They don't go out of their way to sting people. only doing so if a person gets too close to their nest or they feel threatened. Also, you should know that bumble bees do not die after stinging, as some other bees do.

"The "Bumble Bee" is a big, hairy, black and yellow bee whose size can range from 3/4 inch to 1 1/2 inch. This insect is often mistaken for a carpenter bee, which closely resembles the bumble bee in appearance. Carpenter bees have a shiny and smooth abdomen as opposed to the fuzzy abdomen seen on a bumble bee. There are over 200 types of Bumble bees in the world. Fifty different types can be found in North America. Each different species will have its own preference to types of nectar and prefers different flowers."

'The bumble bee is an important, beneficial insect. They pollinate plants and flowers as they forage for food. To gardeners, it is a welcome sight to see these large, flying insects carrying large loads of pollen, flying into and around their flower beds and gardens. While busy searching for food (and at the same time, pollinating plants) bumble bees are rarely a problem when in close proximity to humans. They will actually (in most cases) go out of their way to avoid human contact. Bumble bees will, however, defend themselves if they sense that they are cornered and cannot escape. Most of the time they will fly away from danger but will sting if they are under duress."

Above quote from: http://www.pestproducts.com/bumble-bees.htm