This is one of those things that has bothered me for a very long time, since we started swinging in fact. There is no way I (fem) would EVER expect to enjoy a MFM, or group or swapping or anything that involved sexual contact between me and another person, without allowing my husband to enjoy the same thing from his perspective. NO WAY! And going to clubs and parties and different swing events has shown me that this is VERY common practice .... husband's just stand around while the wives run amock! >
This, to me, is very wrong. And I believe that most, if not all, of these husbands are simply tolerating something that they are not happy with in order to keep their wives happy. Some might call this noble and sacrificing ... I call it selfish on the wives' part and downright stupid on the husband's part.
This is a lifestyle that has no rules, no specifics. You make it what you want out of your comfort levels. But I do agree that it is completely selfish to expect to enjoy what you are not willing to extend to your spouse.
Sorry if this was strong and harsh, but this is something that hits a nerve with me.