I actually use a variation of the Venn diagram in teaching folklore classes. I want to establish that all of us are simultaneously members of more than one cultural group, each of which shares folklore. So the students in my class will have some folklore that overlaps with everyone else in the class ("a stitch in time saves nine" is something that most of them will know), and some folklore that overlaps only with a few of the others or none at all (family lore, hobby group lore, etc).

A diagram is helpful because usually students think of ethnicity and sometimes religion as the only relevant cultural groups they belong to "I'm a Mormon," or "I'm Italian." But they don't think about the fact that their culture is not the same as that of other Italians or other Mormons, because they are ALSO a theatre arts major, science fiction fan, from southern New Jersey, and nineteen years old (for example), each of which is a cultural group that overlaps with all the others. Of course, you can't fit ALL these groups on a venn diagram, but it is a useful starting place.