Conference Behavior

I think this is funny.  So you give a speech at a conference, and afterwards a couple comes up to you and hands you a business card, saying (essentially) "care to join us?"  For details and the card see here.   Question:  when should moronic behavior be treated as private vice, to be discouraged informally; and when should moronic behavior be proscribed by the quasi-legal standards of a community (official conference policy, in this case); and when should moronic behavior be flat out illegal?   Hmm.  This would be a fun case for someone who teaches sexual ethics (alas, I don't).