This is in Australia, but could just as easily happen here: http://www.smh.com.au/nsw/video-captures-sydney-cyclist-crashing-into-car-windscreen-20141027-11cbvd.html
"Without this video evidence and photos, it was highly likely that the actual thing [court case] was going against me rather than the driver."
With ever increasing traffic, and the risk of an accident, it could be sensible. And not just for potential incidents with vehicles but pedestrians also.
Go Pros and the like are pretty cheap these days.