[rcoreyus]

For most people sex and love are intimately tied together, and romantic love is something that they can only feel for one person at a time. For some though, sex is an activity that they enjoy, and if a couple agrees, there is no reason they shouldn't enjoy this with someone else. Its easy to see the appeal of the variety - I suspect that many people at least fantasise about someone other than their partner.

There are some people who can really feel romantic love for more than one person at a time, so it seems natural for them to be intimate with more than one person.

I think that in some cases an open relationship can work well, but that it probably isn't a good idea for the majority of couples.