I've been plotting a contingency plan for shooting people, just in case some confronts me. It involves three things.

1) A business car with my name & url on it.
2) A pack of sample prints on me at all times.
3) An offer for a free 5x7 of any photo I've taken where the person is the subject.

See, bomb defusion & marketing strategy all in one. Granted, I don't have business cards made up yet to test this, but I do carry sample prints and those have helped me in plenty of situations. (Mostly to put digiheads in their place when they ask me why I use what I use.)