How Do You Stop People from Mooching Your Weed?

At a social event, smoking privately can be as tough as old boots. People come in from all directions gathering together drinking each other’s drinks, taking a drag off whoever has a blunt, and so on. Taking advantage of the situation mooches go around enjoying other people’s weed without bringing any themselves, you’ll see people you’ve never met before faking being friends with you just to get your kush off you. In this kind of situation, how can one avoid being taken advantage of by mooches?