I saw people suitcasing at a trade show recently. What ethical obligation do I have to tell show management?

For those unfamiliar with the term, suitcasing refers to nonexhibitors who go to a show as an attendee, but pass out information, samples, etc. about their business from a suitcase, literally or figuratively. But what you were really witnessing was theft from show management, exhibitors, and even attendees. Suitcasers didn't pay to exhibit, and yet they're enjoying access to attendees just the same as legitimate exhibitors.

If you turn a blind eye and don't report it, you are in a small way aiding and abetting the suitcaser, which creates a kind of snowball effect that adversely touches everyone who pays to exhibit or attend. Ultimately, suitcasers can siphon revenues that legitimate exhibitors might have received. If that happens to them enough, those exhibitors may chose not to return to the show, thus making it less effective for attendees. The fewer attendees who come, the fewer exhibitors who show, and thus a vicious circle is born. By not reporting it, you're allowing the suitcaser to undermine the show at which you paid to attend or exhibit. It's in your self-interest as well as everyone else's interest, to alert show management about the suitcaser.