Using a video camera was pretty good for me as it allowed me to improve my own riding more than anything. There were a few instances where cars did stupid things but re-watching it I could have been in a different position and avoided it. Ok so they made a mistake but it was good for me to learn more about how to avoid things like that.
I did this, expecting to scare myself into riding more cautiously, but when I watched the video back it was pretty boring (bar some idiot buzzing a pedestrian through a red light and then getting into an argument with an Audi) so I have upped my RLJing and gap-squeezing accordingly.
Repeat after me: Boring is good
Still fucking boring tho...