I think it's worth highlighting that, even if you think you are doing something entirely legal, when a customer mentions your product or service in the context

I think it's worth highlighting that, even if you think you are doing something entirely legal, when a customer mentions your product or service in the context of their illegal operation, you need to politely ask them to leave and sever the relationship, as a matter of self defense. Take, as a cautionary tale, the case of people teaching other people to beat polygraph tests. http://www.mcclatchydc.com/2013/08/16/199590/seeing-threats-feds-target-instructors.html http://www.mcclatchydc.com/2013/08/16/199590/seeing-threats-... Legal and interesting, but when a "customer" shows up and says "wow, this will really help me beat my government polygraph test", you're apparently supposed to know that that they're talking about an illegal act and that you're being set up. It sucks, but there it is. Paranoia might lose you some business, but there are worse things.