Oh, and here's a "test" that one of my friends uses to distinguish poly from pure swinging (because there truly is a lot of crossover):
Would you let them/him/her know if you were in an accident? Would you invite them/him/her to the family cookout? Would you introduce them/him/her to your vanilla friends? (but not necessarily as sexual buddies, just as other friends...98% of us in these Lifestyles are never intending to "out" ourselves as anything other than monogamous)
If you can answer yes, then you are also Polyamorous in some form. There is more there than just casual sex.
