Nice photo. I would guess it is harvesting fluff for a nest. Watch out for beatles that go inside the tomatoes and make them stink like a landfillThere are usually a pair of them, and they are pretty quick, moving to the other side of the plant if the camera gets too close - which makes me think beneficial? Unless it's clearing off a spot to start gnawing on the plant...
Any pests can do harm if given enough time to colonize. The hoppers just do it faster with a larger feeding habit.Planthoppers can do a lot of harm from what I understand.