That they capture your best, worst and every movement....
Here's probably the stupidest thing I've done on my bike in a very long time. This was Thursday evening riding just having left work for the day:
http://www.youtube.com/watch?v=ZhPMnClvnTU
I tried to time the captions to illustrate what I was actually doing. I'm usually so careful and attentive, but this was a mixture of not double checking and overload of things/environmental things that I needed to take in/watch for.
Tracks were a major concern, and because there was traffic moving in front of me, having just cleared a stray car leftover from the previous opposite light cycle, I thought I was OK.