Evan, you hit the nail on the head!! LOL
Maybe they don't have an ecological impact, I don't know, but I do know this:
They were supposedly introduced into Canada to control the aphid population and quickly moved south. In their native habitat (China, I think) they live/flock/swarm to the sides of large rocky cliffs. About 6 years ago when they first appeared in the midwest, I can remember seeing millions of them swarming around a couple 20 story buildings (resembling cliffs) one warm fall day.
Also, they do bite some people, but not others for some reason (not me, thank goodness) and I guess it doesn't feel too good.

Ecologicly, they could become a problem as it's my understanding they have no natural predators in the US (they taste bad to birds and other animals that would eat them). So, yeah, way to go America...worry about it when it becomes a problem.

LOL