I once mentioned to a friend that I carried two small cameras (a Nikon still camera and a Sony HD video camera) in my coat pockets at all times so that I would never have to say, "Damn, I wish I had a camera right now."
He asked if I ever actually used them.
I told him that it didn't happen often, but, yes, I did stumble upon things to take pictures of: The LoveFest/LoveParade, the Maltese Falcon docked at Pier 35, the police clampdown on Halloween in the Castro a couple of years ago. And to me, those rare occasions justify carrying the cameras.
So when I heard Friday about the zip line stretched across Justin Herman Plaza from now until April 18, all I had to do to get shots of it was to stop by on my way home from work.