Not naive. Doesn't matter if you go at it from a moral perspective, or from a Game Theory perspective (the school that led to MAD and the Prisoner's Delimmae), or from a religious perspective. I think of it as reversing local entropy; increasing the niceness level of the universe. The person you help will at some point help another. The person you trust will trust another, and it goes forth from there. Don't let a few "users" force you into behavior that brings the whole system down.