I've taken the plunge and created an SL group, the rather prosaically titled "Prim Breast Users".
As the charter says, we know that those 25 slots for group membership are precious, but if you use prim breasts, we hope you'll join the group. Here's what I hope: I hope that all of you who use prim breasts will join, so that we can show we're a significant market in SL.
Then we can go to mainstream SL clothiers and say "Look! There are at least [fill in blank] people in SL who use prim breasts, and are cut off from the cornucopia of mainstream SL fashion. They'll be especially appreciative if you accomodate them, whether by adapting the textures of your tops yourself, or by entering into an agreement with one of the growing number of clothiers who specialize in tops for prim breast users."
We can go to animators and show them there are people out there who will appreciate animations and poses that don't leave us with our arms going through our breasts.
We can go to prim breast makers and urge them to work together to make it easier for us to find quality clothing, no matter whose prim breasts we prefer.
If you use prim breasts, please consider joining.
UPDATE: If you'd love to use prim breasts, but don't for some reason, please join too and let me know what's keeping you from it.