Is Open Marriage Hip?

Perhaps it's a trend -- the next trucker hat -- or perhaps it's an elaborate joke, I don't know, but I can't help noticing that when you search Friendster for "open marriages" in the NY area, there are tons of them, particularly in Brooklyn among people in their 20s. What's up with that? Is it for real? If so, how could that be, as open marriages really go against the grain in this country (trust me)? I sort of think that most of the people who list themselves thusly are doing so only because they think it's funny in an absurdist way. Or maybe, it really is hip these days. Anyone have any idea?