Okay, now more than ever, I strongly believe in this (especially after reading Juan 2-8 Mi's post):
If you don't already have one, GET A VIDEO CAMERA AND MOUNT IT TO YOUR HANDLEBARS OR HELMET WHENEVER YOU RIDE.
1) If nothing else, you can get some really cool footage of your surroundings.
2) You never know when you'll see something interesting/bizarre happen that you want to preserve for posterity.
3) And most importantly, if you ever need evidence!
#3 was almost the case for me this morning on the new "Glenwood Greenway," as it's apparently being called. I came to a complete 100% stop at, I think, Bryn Mawr, and after I pulled out into the intersection, the woman on the eastbound side decided it'd be a dandy idea to do the same. Came within inches of hitting me.
Had she actually hit me, she could have been in some serious trouble thanks to camera footage of me coming to a complete stop and proceeding within the bounds of the law.
You don't even need anything expensive like a GoPro or anything like that. My camera is an Ion Air Pro that I got for maybe $30 on Amazon, via DealMac.com. (A lot of times those deal aggregators come up with some really good stuff.) Not the greatest camera in the world, but the video is very clear (fisheye lens though) and it's a pretty sturdy camera. Only problem is that the threads where the mounting screw goes are made of plastic, so you gotta be careful there.