Haha, James! You've been Googling again, haven't you?
The queen does use her sting for that one, sinister purppose. In a queenless hive, there will be a number of "queen" cells. When the first virgin queen is about to emerge, she 'pipes." When more queens try to emerge, though, their piping causes the first born queen to sting them through the wax covering of their cells. Gives a whole new dimension to "sibling rivalry," dunnit? Still, to be fair, she kills off all her daughters as well. I'm not sure where you got the idea of multiple queens in one hive, though. The only time I've seen that is on those big hives that contain several, seperated colonies. Only one queen per colony, though.