Oh you've got to be kidding me.
Stories like this anger me to the absolute max, the thought of the Police taking the internet bragging of a 19 year old so seriously would be laughable if it weren't so sad.
It's the internet for Christ sake. People lie and B.S on forums, especially rich spoiled teenagers.
The method of the Police corroborating the story is epic too. Canvassing a neighbourhood - What the hell is that going prove? Unless one of them just happened to be playing around with their fully calibrated Gatso device at the time, nothing. And What exactly is this witnesses' statement? "He was going fast"? How do you know? People's perception of speed is crap, especially when loud noises (Like a M5 under hard acceleration) are involved.
Not saying the guy didn't do it, he obviously did if he's wimped out like this, but the authority's "If it was posted on the internets, It must be true!" stance is nothing short of ridiculous. Any forum user who used such a stance would be drown in a sea of male cow dung!