[FateAmenableToChange]

I wonder if the increase in Yellow Jacket activity has to do with the reduction in the Honeybee population:

Yellow jackets eat honeybees. I've seen one yellow jacket kill 15 or 20 bees while raiding one of my hives.

[Hacksaw]

According to the literature I have read, yellow jackets are considered beneficial because they eat crop destroying bugs (except for the honeybees I guess). The drawback of course is that they are very agressive. Smashing one will release a scent which will cause others to attack.

Yellow Jacket Fact Sheet