Pre-9/11 there was a time when I could copy your plate # down, go into my local precinct, give them your plate # and tell the officer on duty that you hit my car and a witness watched you drive away. I want your info so I can go to your house and tell you what you did. Pre- 9/11 a cop would release your address to me w/o issue (I've done this plenty of times to know it works)...
Post-9/11 they won't do a damn thing besides investigate the matter themselves...