[aurora]

Yes, indeed the Ds poly is a fairly small population in the community as a whole. And a successful poly dynamic is always based upon the feelings and needs of everyone involved. But within the BDSM community, where there are situations where the power exchange allows (with previous agreement) one member of the family to make choices for the others that would normally have to be negotiated continuously, there is the room for imposed additions. And, from what I have seen, even though the submissive members have given consent to whatever is to happen, it does not work out well if the new person is brought in without full, whole-hearted agreement from the more senior members.
Also, some of the Ds poly situations are more loosely-knit leather families where most live in other cities and are not in the same house...in this case the poly family members might feel a loss of extra communication with the Dom(me) when a new member is added, but are not in the day-to-day sharing the bathroom type communication with the other family members.