Now the purpose of the deflector dish on a starship is to push aside debris and objects in the ships path so that when the ship is moving it doesn't plow through this debris and destroy the ship. This debris that gets flung aside is subject to the laws of physics in space and will keep moving, eventually becoming subject to other forces.
As we are learning, space is not nearly so empty as we used to believe. With millions of ships throughout the galaxy flinging debris in every direction, would not this near infinitesimal amount of debris being flung about become an extreme hazard to other ships, space stations and inhabited worlds? Technologically advanced worlds would have various defenses to protect them from this, but most of the inhabited worlds in the Star Trek universe have not developed to the point of having such advanced space based technology.
So would this not be danger to them? And has this potential danger ever been addressed in any of the stories? I'm pretty sure it was never discussed in any of the tv series, but perhaps one of the books?