It's late and I'm tired so please forgive me if this doesn't make as much sense as it did in my head before I wrote it out here.
I think it's possible for some to love more than one person at once. The only thing is, for it to be completely mutual and for the relationship to be successful in this type of setting the other person(s) in the relationship has/have to be comfortable with the fact that there will be another spouse in the equation. More over, all parties have to form a bond and healthy relationship (not talking strictly sexual in nature) with each other for it to be completely successful. Jealousy can not over rule the relationship from any one party.
It's incredibly difficult to balance all involved relationships and keep them healthy and there are those that have done it and are still doing it successfully.
It's just one of those things that not everyone's into and that's ok too. I just think that everyone is entitled to love and if that means that they want more than one spouse at a time and all parties are willing and capable and accepting of that fact then anything is possible.
FWIW I can't imagine having a bed filled with all married parties in the same space. That would be creepy and the morning breath would be horrible BUT generally polygamists don't (at least as far as I know) generally all share the same bed together at once or at all. I'm pretty sure while they may share the same household, each have their own rooms and space.
If I had to do it, I think I'd look more at the pros than the cons. For instance, you're always going to have someone to help watch your children when you need something or when you need a moment to yourself (on a rare occasion.) You're always going to have really close best friends (provided you aren't the jealous type and if you are polygamy isn't for you). You'll never be completely alone ever because you'll have this huge family and a circle of people who love you and who you love in return.
Again, it's not for everyone but I really do believe that it is possible to love more than one person at a time. I just think that in many societies today it is frowned upon and generally not accepted even my government standards. In that regard, I think it's unfortunate that some governments have a say in who gets to love who and how many whos ( I feel like I'm talking about Dr. Seuss characters here) you can love at once. But then again, there's another discussion going on somewhere around here about gay/lesbian marriages and interracial marriage, so there's another few examples of the government getting in the way of people's personal preferences on love.
Alright this topic is sounding more and more strange as I type it so I better just leave it at that before some nice person comes along to tell me how horrible my explanation has been.