I've started thinking - and I'm serious here, no joking - that there is a side to having multiple husbands/wives that makes sense today.
Economically, it may be beneficial. There are a lot of people today barely making it. If they had 2 or 3 more adults in the family unit, it could relieve financial stress (assuming everyone involved shares the same goal/plan).
Think about it. Regardless of the make up, when kids come... one of our very own gripes here is that nobody is taking time to raise and teach kids anymore. Well, if you had 3 adults working and 1 at home raising the kids, maybe this would get better. Moms and Dads wouldn't have to pay for child care - which is expensive from what I hear. Someone would be available to run errands during the week, take kids to Dr., get cars repaired, etc.. (less time away from work for the others).
Plus, it's generally cheaper to buy one big house than 2 or 3 smaller houses. I think it could work and be beneficial to todays broke, over stressed, no time to properly raise kids family. But I admit it could be a legal mess if one decided to leave (or the others decided to kick one out). But it would be interesting to see a family put my theory into practice and see if it works.
And all that aside... if everyone is a consenting adult, I say "why not?" It's not like anyone is staying loyal and making the traditional family unit work these days anyway.