Actually I think it depends what state you are in what the police will do.
I had somebody throw rocks at me while jogging. I reported their numberplate but there was no way to prove it as I didnt photograph them or anything. The police contacted the owner of the car and had a chat to them. I think this is a good idea as they arent being charged as such but they know that they cant get away with that behaviour either - if there are more reports from other people then obviously the person will be followed up. But also if the police only talk to them they get to say their side if, for example I had the number plate wrong.