Hmm. These are challenging issues.
I'll chime in from the perspective of an ethically non-monogamous single-by-choice 30-ish straight female who enjoys being (and having) a friend-with-benefits or casual-but-steady-partner or lover or secondary or whatever.
If I have a FWB who has other lovers, I would NOT AT ALL be okay with him giving out my contact info to his other lovers.
I would NOT appreciate being contacted with one his others--I would find it remarkably weird and an invasion of my privacy.
I would be uncomfortable with the friendly, simple email that GalaGirl suggested. If I sleep with a friend occasionally, I don't need to hear from everyone he sleeps with.
If I were concerned about health issues, I would not be in a non-exclusive relationship.
I wouldn't mind becoming friends with my FWB's others in the right circumstances, but it's not remotely necessary.
Independence, free-spirited-ness and a certain degree of separateness are why I choose FWB relationships in the first place. I don't need to know everything about him and his life.
I don't consider my FWB's lovers any of my business. He's a friend of mine that I sleep with. We have fun together, are supportive of and honest with each other, and otherwise we stay out of each other's way.
I don't care who my platonic friends are friends with; why would I care who my FWB is also FWB with?
A similar sentiment might be behind Q's (3quarks) remark about "not giving a shit about his other lovers." It's not that she doesn't care about them as people; she just doesn't consider it any of her business. It's not relevant to her.
Sometimes if I grow closer to a lover or see him frequently enough that we become more involved with each other, I naturally learn more about his other partners or maybe end up meeting them. But it's not a requirement.
I would find it absurd if my lover said, "One of my other lovers needs to meet you because her husband is worried that I'm not being honest with you."
In that situation, I would have to say, "No thanks, the husband can work out his trust issues on his own."
I do understand where you're coming from, Undermind. I know that Q created a difficult situation by cheating on you in the past.
But it's condescending of you (Undermind) to assume that just because a guy has multiple casual partners, they must not be giving full consent!
There is nothing in what you've said about D that makes him sound like he's being dishonest with his various women. I suspect they can tell pretty easily that he's not a one-woman guy. I suspect D seeks out women who do not want a monogamous relationship.
It sounds like you don't actually understand why some people like and seek out more casual relationships. It may help if you think of those relationships as friendships. It's really NOT just about the sex. But maybe it IS about having relationships that stay at the friendship level, not at the committed-romantic-partner level.
It's fine if you're not okay with having those types of relationships yourself. But your wife doesn't feel the same way. Why do you need to restrict what she wants just because you're having trouble understanding it?
Undermind, your contempt for D really comes across. You just can't fathom why someone would have casual partners, FWBs they see irregularly, etc. And you seem shocked that D has so many partners (whereas really, it just sounds like has a handful of friends that he sees with varying frequency).
3quarks, I wouldn't want to be in your shoes. I know you want to respect your husband's limits and make him feel comfortable.
But Undermind, I think you need to do a little more work to feel more at ease with people who have friendship-sex/casual sex friends.
Single, straight, female, solo, non-monogamous.