A mate of mine used to commute via roadbike through London. One day he was knocked off his bike, he was fairly badly hurt, his bike was in pieces. Insurance and police couldn’t do a thing as there was no proof. He asked if video proof would be sufficient, and they agreed it would
He now films all trips with a Contour I think. He uploads all poor driving to youtube, and has had some drivers contact him to take down the evidence as it shows their number plates! He checked site regulations and was ok to keep footage up.
He’s had some success with forwarding awful driving to the police, and they’ll go and breathe down someone’s collar if they’ve been driving particularly badly.