I tried this 7 years ago. It's real hard and it's never a pleasant fall. I think it's a hippy sport like Frisbee Golf. My friend who was getting into it was a rock climber and kind of a naturalist type. He had a flavor savor, that's pretty much all you need to know.
People are always doing it in Balboa park. You take the slack rope and tie it between two trees and then get funky.
Here's an example:
HIgher degree of difficulty after the jump.