In years past, it was a common practice I guess, because there weren't that many opportunities for women, and it was better than other alternatives. I don't know how much of the Old Testament is true, but it is said that Abraham, Jacob, David, Solomon, and others all had multiple wives. I think Solomon was supposed to have 700 wives and 300 Concubines. But alas, it didn't end well for him.
In today's world, women have many more choices, and except in rare cases, I would think that wouldn't be an acceptable arrangement. I suppose if you had the right mix of people, who weren't the jealous or possessive type, perhaps they could make it work (Albeit outside of public scrutiny). I guess to each his own, but it sounds like a recipe for trouble to me.