When a yellowjacket stings you, it also sprays the wound with a scented chemical that tells other yellowjackets to land on you and sting the same spot. The smell is detectable by other yellowjackets up to 30 yards away.
If you want to take out a whole nest of yellowjackets quickly, go down to the liquor store and buy a big bottle of everclear (the 95% alcohol that you spike punch with). Take that bottle out behind your house where the nest is, pour it down into the nest, and then stomp on the hole or put a stick in it. You'll kill every one of them.
(Note, however, that you'll probably see a resurgence of other annoying bugs in the area after they're gone.)